Pcbnew: very minor fixes and update:  update clipper version. uncrustify polytri/* and fix some warning compil.

Switch to boost::context for all platforms, almost.
Please try your platform by commenting out fcontext.s in common/CMakeLists.txt.

[MacOSX] fixes issues with previous OSX compilers gcc-4.2 and makes a better general beaviour of KICAD_BUILD_STATIC

eeschema: fix compil issue. Boost build: boost lib context built only on OSX (does not build on mingw, and not needed)

(https://svn.boost.org/trac/boost/ticket/8266)

Move HitTestForCorner and HitTestForEdge code from class_zone to polygon/PolyLine.cpp, to avoid redundant code.
Fix bug 1264248.
Fix a very minor issue in RemoveTrailingZeros, for countries where the separator in floating numbers is a comma.

Dialog fp plugin option: Fix compil issue under gcc 4.4 (does not happen with 4.6 and later) about an overloaded function.

Update freedesktop files according to http://standards.freedesktop.org/desktop-entry-spec/desktop-entry-spec-latest.html

add mime type application/x-pcbnew-pcb, extend Desktop Exec to support a file to open on command line

specctra_export.cpp: Fix a conversion error from mils to mm I made i n may last commit, which set min dist to find a segment end for internal outlines holes to 1 mil instead of 10 mils.