gl:  THIS IS LIKE HACK.  Make msaa compositor works on HD3000/HD4000

Mesa 9.1+ supports GLESv3, but does not support GL_ANGLE_framebuffer_blit
and GL_ANGLE_framebuffer_multisample.  However, these two extensions
have been part of standard GLESv3 functions.  So if the driver supports
GLESv3, it is almost certain, it also supports these two extensions.

we will drop this once GL_ANGLE_framebuffer_blit and
GL_ANGLE_framebufer_multisample are supported