GITHUB_PLUGIN uses redirected URL to remove one HTTP hit time.

* Pcbnew: catch exceptions when saving changes to footprint library table.
* Pcbnew: update footprint viewer library list if open when footprint library
  table changes.
* CvPcb: update library list when footprint library table changes.
* Minor coding policy fixes.

*) Move button handlers to LEFT MOUSE CLICK from COMMAND events, so wxGrid focus is not lost.
*) Sketch out the concept of COW support for the GITHUB_PLUGIN in its @todo.

https://svn.boost.org/trac/boost/ticket/8973
https://svn.boost.org/trac/boost/changeset/84950#file0

This is so builders with multiple out of source build trees can all use
the same common boost install directory.  And the build system will not
vascillate between the fuller and lesser subsets of boost.

All: under mingw32+msys: fix an issue when using Cmake version >= 2.8.5 which uses by default a response file.
This response file is not expanded under mingw3 2 (mingw/gcc bug?), and the list of include paths, found in this file, is not taken in account.
Now, under mingw32+msys, when not cross-compiling, the response file is disabled.
Cvpcb, Pcbnew: fix a list of libs  which should be added only when cross-compiling:
Previously, they were always added, which creates an issue with mingw/msy/ gcc  2.8.
Now they are added only when cross-compiling (this issue was noticeable only with msys+mingw version  2.8)

* Replace all occurrences of the word "part" with "unit" when referring to
  multiple unit components for improved consistency.
* Replace "shared by" with "common to" when referring to objects (lines, arcs,
  pins, etc.) that are common to all units.
* Improve wording in library component properties dialog.

* Build OpenSSL from source using the OpenSSL-CMake project on Windows with MinGW when no specifying OPENSSL_ROOT_DIR

Mingw, all: remove static link of libgcc, which can create issues when using dll version of wxWidgets.
Therefore libgcc_s_dw2-1.dll should be in the paths for executables.

add libglew-dev prerequisite for debian systems, it pulls in libgl1-mesa-dev and libglu1-mesa-dev on its own

Fixes missing worksheet layout when there is no PCB loaded and all random brightness changes for the Cairo rendering backend.

Pcbnew: Fix incorrect bounding box calculation of texts. Only noticeable with boards conveted from Eagle, which are using other text justification than center.
Eagle plugin: filter and replace not allowed chars in FPID(-':' and '/')  by _ or -, if they are used in Eagle footprint names (otherwise, boards converted and saved under kicad_pcb format are not readable by Pcbnew).

Disable patch from Baranovskiy Konstantin about vertical justification of multiline texts, because it does not work for rotated/mirrored texts

   pass into an HTML rendering panel and otherwise look goofey.
*) Implement BOARD::Move() can call it from EAGLE_PLUGIN::Load().
*) When USE_FP_LIB_TABLE, tolerate blank nicknames in FPIDs coming from eeschema.
   See the switch for this in pcbnew/netlist.cpp as ALLOW_PARTIAL_FPID.
*) Add an assert and a try catch block to figure out that View does not
   like some eagle pcb board.  bitset::set() is getting a -1 value and firing
   an exception.

Pcbnew, compiled with python support: Under windows, force python environment, if the folder python27_us is found in Kicad bin folder (<kicad>/bin, and if  python27_us environment is not fully set (i.e. if python27_us is not in the path, or if PYTHONPATH id not defined.)

<%s> being replaced with '%s' because the former in invisible in html panels.
Cure some compiler warnings.