The ARB_sync api depends on a GLsync type which may not be available if
GL_ARB_sync isn't defined, such as when building for gles2 only. This
guards the prototypes with #ifdef GL_ARB_sync to fix compilation when a
GLsync type isn't defined.
Reviewed-by: Neil Roberts <neil@linux.intel.com>
(cherry picked from commit ba79020e0f5b102e8b25cd831c408dd68d241297)
d39f4b8a16