Fix build issues on MinGW when finding OpenSSL.

* Add FindOpenSSL.cmake from CMake 3.0.2.
* Change MinGW find library to find libssl and libcrypto as well as libeay32 and ssleay32.  Apparently
 at some point OpenSSL changed the library file names for MinGW.
* Stop find_library() from looking in system paths and returning the actual DLLs rather than the link
  libraries.

CMakeModules/FindOpenSSL.cmake

+#.rst:
+# FindOpenSSL
+# -----------
+#
+# Try to find the OpenSSL encryption library
+#
+# Once done this will define
+#
+# ::
+#
+#   OPENSSL_ROOT_DIR - Set this variable to the root installation of OpenSSL
+#
+#
+#
+# Read-Only variables:
+#
+# ::
+#
+#   OPENSSL_FOUND - system has the OpenSSL library
+#   OPENSSL_INCLUDE_DIR - the OpenSSL include directory
+#   OPENSSL_LIBRARIES - The libraries needed to use OpenSSL
+#   OPENSSL_VERSION - This is set to $major.$minor.$revision$path (eg. 0.9.8s)
+
+#=============================================================================
+# Copyright 2006-2009 Kitware, Inc.
+# Copyright 2006 Alexander Neundorf <neundorf@kde.org>
+# Copyright 2009-2011 Mathieu Malaterre <mathieu.malaterre@gmail.com>
+#
+# Distributed under the OSI-approved BSD License (the "License");
+# see accompanying file Copyright.txt for details.
+#
+# This software is distributed WITHOUT ANY WARRANTY; without even the
+# implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+# See the License for more information.
+#=============================================================================
+# (To distribute this file outside of CMake, substitute the full
+#  License text for the above reference.)
+
+if (UNIX)
+  find_package(PkgConfig QUIET)
+  pkg_check_modules(_OPENSSL QUIET openssl)
+endif ()
+
+if (WIN32)
+  # http://www.slproweb.com/products/Win32OpenSSL.html
+  set(_OPENSSL_ROOT_HINTS
+    ${OPENSSL_ROOT_DIR}
+    "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\OpenSSL (32-bit)_is1;Inno Setup: App Path]"
+    "[HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Uninstall\\OpenSSL (64-bit)_is1;Inno Setup: App Path]"
+    ENV OPENSSL_ROOT_DIR
+    )
+  file(TO_CMAKE_PATH "$ENV{PROGRAMFILES}" _programfiles)
+  set(_OPENSSL_ROOT_PATHS
+    "${_programfiles}/OpenSSL"
+    "${_programfiles}/OpenSSL-Win32"
+    "${_programfiles}/OpenSSL-Win64"
+    "C:/OpenSSL/"
+    "C:/OpenSSL-Win32/"
+    "C:/OpenSSL-Win64/"
+    )
+  unset(_programfiles)
+else ()
+  set(_OPENSSL_ROOT_HINTS
+    ${OPENSSL_ROOT_DIR}
+    ENV OPENSSL_ROOT_DIR
+    )
+endif ()
+
+set(_OPENSSL_ROOT_HINTS_AND_PATHS
+    HINTS ${_OPENSSL_ROOT_HINTS}
+    PATHS ${_OPENSSL_ROOT_PATHS}
+    )
+
+find_path(OPENSSL_INCLUDE_DIR
+  NAMES
+    openssl/ssl.h
+    ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+  HINTS
+    ${_OPENSSL_INCLUDEDIR}
+  PATH_SUFFIXES
+    include
+)
+
+if(WIN32 AND NOT CYGWIN)
+  if(MSVC)
+    # /MD and /MDd are the standard values - if someone wants to use
+    # others, the libnames have to change here too
+    # use also ssl and ssleay32 in debug as fallback for openssl < 0.9.8b
+    # TODO: handle /MT and static lib
+    # In Visual C++ naming convention each of these four kinds of Windows libraries has it's standard suffix:
+    #   * MD for dynamic-release
+    #   * MDd for dynamic-debug
+    #   * MT for static-release
+    #   * MTd for static-debug
+
+    # Implementation details:
+    # We are using the libraries located in the VC subdir instead of the parent directory eventhough :
+    # libeay32MD.lib is identical to ../libeay32.lib, and
+    # ssleay32MD.lib is identical to ../ssleay32.lib
+    find_library(LIB_EAY_DEBUG
+      NAMES
+        libeay32MDd
+        libeay32d
+        ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "VC"
+        "lib/VC"
+    )
+
+    find_library(LIB_EAY_RELEASE
+      NAMES
+        libeay32MD
+        libeay32
+        ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "VC"
+        "lib/VC"
+    )
+
+    find_library(SSL_EAY_DEBUG
+      NAMES
+        ssleay32MDd
+        ssleay32d
+        ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "VC"
+        "lib/VC"
+    )
+
+    find_library(SSL_EAY_RELEASE
+      NAMES
+        ssleay32MD
+        ssleay32
+        ssl
+        ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "VC"
+        "lib/VC"
+    )
+
+    set(LIB_EAY_LIBRARY_DEBUG "${LIB_EAY_DEBUG}")
+    set(LIB_EAY_LIBRARY_RELEASE "${LIB_EAY_RELEASE}")
+    set(SSL_EAY_LIBRARY_DEBUG "${SSL_EAY_DEBUG}")
+    set(SSL_EAY_LIBRARY_RELEASE "${SSL_EAY_RELEASE}")
+
+    include({CMAKE_CURRENT_LIST_DIR}/SelectLibraryConfigurations.cmake)
+    select_library_configurations(LIB_EAY)
+    select_library_configurations(SSL_EAY)
+
+    mark_as_advanced(LIB_EAY_LIBRARY_DEBUG LIB_EAY_LIBRARY_RELEASE
+                     SSL_EAY_LIBRARY_DEBUG SSL_EAY_LIBRARY_RELEASE)
+    set( OPENSSL_LIBRARIES ${SSL_EAY_LIBRARY} ${LIB_EAY_LIBRARY} )
+  elseif(MINGW)
+    message( STATUS "Searching for OpenSSL in MinGW." )
+    # same player, for MinGW
+    set(LIB_EAY_NAMES libeay32)
+    set(SSL_EAY_NAMES ssleay32)
+    list(APPEND LIB_EAY_NAMES crypto)
+    list(APPEND SSL_EAY_NAMES ssl)
+
+    find_library(LIB_EAY
+      NAMES
+        ${LIB_EAY_NAMES}
+      ${_OPENSLL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "lib/MinGW"
+      # Do not search system path.  Otherwise the DLL will be found rather than the link library.
+      NO_SYSTEM_ENVIRONMENT_PATH
+      NO_CMAKE_SYSTEM_PATH
+    )
+
+    find_library(SSL_EAY
+      NAMES
+        ${SSL_EAY_NAMES}
+      ${_OPENSLL_ROOT_HINTS_AND_PATHS}
+      PATH_SUFFIXES
+        "lib"
+        "lib/MinGW"
+      # Do not search system path.  Otherwise the DLL will be found rather than the link library.
+      NO_SYSTEM_ENVIRONMENT_PATH
+      NO_CMAKE_SYSTEM_PATH
+    )
+
+    mark_as_advanced(SSL_EAY LIB_EAY)
+    set( OPENSSL_LIBRARIES ${SSL_EAY} ${LIB_EAY} )
+    unset(LIB_EAY_NAMES)
+    unset(SSL_EAY_NAMES)
+  else()
+    # Not sure what to pick for -say- intel, let's use the toplevel ones and hope someone report issues:
+    find_library(LIB_EAY
+      NAMES
+        libeay32
+      ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      HINTS
+        ${_OPENSSL_LIBDIR}
+      PATH_SUFFIXES
+        lib
+    )
+
+    find_library(SSL_EAY
+      NAMES
+        ssleay32
+      ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+      HINTS
+        ${_OPENSSL_LIBDIR}
+      PATH_SUFFIXES
+        lib
+    )
+
+    mark_as_advanced(SSL_EAY LIB_EAY)
+    set( OPENSSL_LIBRARIES ${SSL_EAY} ${LIB_EAY} )
+  endif()
+else()
+
+  find_library(OPENSSL_SSL_LIBRARY
+    NAMES
+      ssl
+      ssleay32
+      ssleay32MD
+    ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+    HINTS
+      ${_OPENSSL_LIBDIR}
+    PATH_SUFFIXES
+      lib
+  )
+
+  find_library(OPENSSL_CRYPTO_LIBRARY
+    NAMES
+      crypto
+    ${_OPENSSL_ROOT_HINTS_AND_PATHS}
+    HINTS
+      ${_OPENSSL_LIBDIR}
+    PATH_SUFFIXES
+      lib
+  )
+
+  mark_as_advanced(OPENSSL_CRYPTO_LIBRARY OPENSSL_SSL_LIBRARY)
+
+  # compat defines
+  set(OPENSSL_SSL_LIBRARIES ${OPENSSL_SSL_LIBRARY})
+  set(OPENSSL_CRYPTO_LIBRARIES ${OPENSSL_CRYPTO_LIBRARY})
+
+  set(OPENSSL_LIBRARIES ${OPENSSL_SSL_LIBRARY} ${OPENSSL_CRYPTO_LIBRARY})
+
+endif()
+
+function(from_hex HEX DEC)
+  string(TOUPPER "${HEX}" HEX)
+  set(_res 0)
+  string(LENGTH "${HEX}" _strlen)
+
+  while (_strlen GREATER 0)
+    math(EXPR _res "${_res} * 16")
+    string(SUBSTRING "${HEX}" 0 1 NIBBLE)
+    string(SUBSTRING "${HEX}" 1 -1 HEX)
+    if (NIBBLE STREQUAL "A")
+      math(EXPR _res "${_res} + 10")
+    elseif (NIBBLE STREQUAL "B")
+      math(EXPR _res "${_res} + 11")
+    elseif (NIBBLE STREQUAL "C")
+      math(EXPR _res "${_res} + 12")
+    elseif (NIBBLE STREQUAL "D")
+      math(EXPR _res "${_res} + 13")
+    elseif (NIBBLE STREQUAL "E")
+      math(EXPR _res "${_res} + 14")
+    elseif (NIBBLE STREQUAL "F")
+      math(EXPR _res "${_res} + 15")
+    else()
+      math(EXPR _res "${_res} + ${NIBBLE}")
+    endif()
+
+    string(LENGTH "${HEX}" _strlen)
+  endwhile()
+
+  set(${DEC} ${_res} PARENT_SCOPE)
+endfunction()
+
+if (OPENSSL_INCLUDE_DIR)
+  if (_OPENSSL_VERSION)
+    set(OPENSSL_VERSION "${_OPENSSL_VERSION}")
+  elseif(OPENSSL_INCLUDE_DIR AND EXISTS "${OPENSSL_INCLUDE_DIR}/openssl/opensslv.h")
+    file(STRINGS "${OPENSSL_INCLUDE_DIR}/openssl/opensslv.h" openssl_version_str
+         REGEX "^#define[\t ]+OPENSSL_VERSION_NUMBER[\t ]+0x([0-9a-fA-F])+.*")
+
+    # The version number is encoded as 0xMNNFFPPS: major minor fix patch status
+    # The status gives if this is a developer or prerelease and is ignored here.
+    # Major, minor, and fix directly translate into the version numbers shown in
+    # the string. The patch field translates to the single character suffix that
+    # indicates the bug fix state, which 00 -> nothing, 01 -> a, 02 -> b and so
+    # on.
+
+    string(REGEX REPLACE "^.*OPENSSL_VERSION_NUMBER[\t ]+0x([0-9a-fA-F])([0-9a-fA-F][0-9a-fA-F])([0-9a-fA-F][0-9a-fA-F])([0-9a-fA-F][0-9a-fA-F])([0-9a-fA-F]).*$"
+           "\\1;\\2;\\3;\\4;\\5" OPENSSL_VERSION_LIST "${openssl_version_str}")
+    list(GET OPENSSL_VERSION_LIST 0 OPENSSL_VERSION_MAJOR)
+    list(GET OPENSSL_VERSION_LIST 1 OPENSSL_VERSION_MINOR)
+    from_hex("${OPENSSL_VERSION_MINOR}" OPENSSL_VERSION_MINOR)
+    list(GET OPENSSL_VERSION_LIST 2 OPENSSL_VERSION_FIX)
+    from_hex("${OPENSSL_VERSION_FIX}" OPENSSL_VERSION_FIX)
+    list(GET OPENSSL_VERSION_LIST 3 OPENSSL_VERSION_PATCH)
+
+    if (NOT OPENSSL_VERSION_PATCH STREQUAL "00")
+      from_hex("${OPENSSL_VERSION_PATCH}" _tmp)
+      # 96 is the ASCII code of 'a' minus 1
+      math(EXPR OPENSSL_VERSION_PATCH_ASCII "${_tmp} + 96")
+      unset(_tmp)
+      # Once anyone knows how OpenSSL would call the patch versions beyond 'z'
+      # this should be updated to handle that, too. This has not happened yet
+      # so it is simply ignored here for now.
+      string(ASCII "${OPENSSL_VERSION_PATCH_ASCII}" OPENSSL_VERSION_PATCH_STRING)
+    endif ()
+
+    set(OPENSSL_VERSION "${OPENSSL_VERSION_MAJOR}.${OPENSSL_VERSION_MINOR}.${OPENSSL_VERSION_FIX}${OPENSSL_VERSION_PATCH_STRING}")
+  endif ()
+endif ()
+
+include(FindPackageHandleStandardArgs)
+
+if (OPENSSL_VERSION)
+  find_package_handle_standard_args(OpenSSL
+    REQUIRED_VARS
+      OPENSSL_LIBRARIES
+      OPENSSL_INCLUDE_DIR
+    VERSION_VAR
+      OPENSSL_VERSION
+    FAIL_MESSAGE
+      "Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the system variable OPENSSL_ROOT_DIR"
+  )
+else ()
+  find_package_handle_standard_args(OpenSSL "Could NOT find OpenSSL, try to set the path to OpenSSL root folder in the system variable OPENSSL_ROOT_DIR"
+    OPENSSL_LIBRARIES
+    OPENSSL_INCLUDE_DIR
+  )
+endif ()
+
+mark_as_advanced(OPENSSL_INCLUDE_DIR OPENSSL_LIBRARIES)