Add CheckCXXSymbolExists.cmake to fix configure bug using CMake versions prior...

Add CheckCXXSymbolExists.cmake to fix configure bug using CMake versions prior to 2.8.6. (fixes lp:1124854)

CMakeModules/CheckCXXSymbolExists.cmake

+# - Check if a symbol exists as a function, variable, or macro in C++
+# CHECK_CXX_SYMBOL_EXISTS(<symbol> <files> <variable>)
+#
+# Check that the <symbol> is available after including given header
+# <files> and store the result in a <variable>.  Specify the list
+# of files in one argument as a semicolon-separated list.
+# CHECK_CXX_SYMBOL_EXISTS() can be used to check in C++ files, as opposed
+# to CHECK_SYMBOL_EXISTS(), which works only for C.
+#
+# If the header files define the symbol as a macro it is considered
+# available and assumed to work.  If the header files declare the
+# symbol as a function or variable then the symbol must also be
+# available for linking.  If the symbol is a type or enum value
+# it will not be recognized (consider using CheckTypeSize or
+# CheckCSourceCompiles).
+#
+# The following variables may be set before calling this macro to
+# modify the way the check is run:
+#
+#  CMAKE_REQUIRED_FLAGS = string of compile command line flags
+#  CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
+#  CMAKE_REQUIRED_INCLUDES = list of include directories
+#  CMAKE_REQUIRED_LIBRARIES = list of libraries to link
+
+#=============================================================================
+# Copyright 2003-2011 Kitware, Inc.
+#
+# 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.)
+
+include(CheckSymbolExists)
+
+macro(CHECK_CXX_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
+  _CHECK_SYMBOL_EXISTS("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckSymbolExists.cxx" "${SYMBOL}" "${FILES}" "${VARIABLE}" )
+endmacro()