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
pass png_static_libs to other_ldflags in install.gypi on Linux, closes #581
Merge pull request #600 from mapbox/png-other-ldflags

pass png_static_libs to other_ldflags in install.gypi on Linux