Some GLSL-related function prototypes are GLES2-only: GL implementations
are not required to provide them.
While Mesa is perfectly happy to return a dummy function pointer for
functions it doesn't support, other platforms are more picky, and will
return NULL.
In this particular case, this commit fixes GLSL support on OSX.
https://bugzilla.gnome.org/show_bug.cgi?id=668856
Reviewed-by: Neil Roberts <neil@linux.intel.com>
This splits up cogl-ext-functions.h in to sets of prototypes that
can be included separately so that we can include just core
gles1 or gles2 functions without any extensions.
Since eglGetProcAddress can not be used to query core client APIs
and some implementations (notably on Android) can return a garbage
pointer instead of NULL this will allow us to explicitly check
when to use eglGetProcAddress and when to use dlsym().
Reviewed-by: Neil Roberts <neil@linux.intel.com>
