Merge pull request #47 from ybunyak/master

MacOS X examples fixes
OpenGL example: comments on glfw window size vs frame buffer size.
Added IO.FontBaseScale for global rescale. Renamed SetFontScale to SetWindowFontScale
Doc formatting + adding 'API changes' section
Tweak comments following feedbacks.
Added IsMouseHoveringWindow(), IsMouseHoveringAnyWindow()
Added IsPosHoveringAnyWindow()
Moved IM_MALLOC/IM_FREE/etc. to IO structure members one can set at runtime.
Warning fixes (from Andrea Pessino)
Added va_list variations of all functions taking ... parameters (from Andrea Pessino)
Update version number in sources
Renamed section in documentation
Tab to spaces