repair undef None GLX wrapper, pass 0 instead of None to GLX functions
Merge pull request #583 from mapbox/glx-undef-none

repair undef None GLX wrapper, pass 0 instead of None to GLX functions
check library versions against header symbols in static initialization function

fixes #580
Merge branch 'master' of github.com:mapbox/mapbox-gl-native into android-mason

Conflicts:
	platform/default/image.cpp
Fix crash