Pcbnew: fix a build issue when BUILD_GITHUB_PLUGIN is enabled.
error: 'uintptr_t' was not declared in this scope.
https://svn.boost.org/trac/boost/ticket/8973
https://svn.boost.org/trac/boost/changeset/84950#file0
Escape " character to fix warning in TokenList2DsnLexer.cmake
*) Add PLUGIN::FootprintLibOptions( PROPERTIES* ), and extend DIALOG_FP_PLUGIN_OPTIONS to use it.
*) 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.
Footprint library table fixes.

* 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.
wxString PCB_BASE_FRAME::SelectFootprintFromLibBrowser() now returns empty string on abort.
GITHUB_PLUGIN uses redirected URL to remove one HTTP hit time.