Headers gl2.h and gl2ext.h shipped with NaCl are different to the
official ones, which is causing linker issues, thus using NaCl's own
gl2.h. They are otherwise similar, thus it should cause no compatibility
issues.
On the other hand, gl2ext.h shipped with NaCl is slightly outdated with
some recent extensions missing. We are including the NaCl's one and then
the official one over it (undefining the include guard). The symbols are
guarded also by extensions, so it should cause no conflicts.
Vladimír Vondruš
cdbc12821f