Add unpublished APPLE_flush_render extension.
Add unpublished APPLE_flush_render extension.

bclemetsonblizzard/vogl,kingtaurus/vogl,ValveSoftware/vogl,bclemetsonblizzard/vogl,kingtaurus/vogl,ValveSoftware/vogl,ValveSoftware/vogl,ValveSoftware/vogl,bclemetsonblizzard/vogl,kingtaurus/vogl,kingtaurus/vogl,bclemetsonblizzard/vogl,bclemetsonblizzard/vogl