i965/dri: Turn on support for image modifiers
i965/dri: Turn on support for image modifiers

All the plumbing is in place so the extension just needs to be
advertised.

Signed-off-by: Ben Widawsky <73675debcd8a436be48ec22211dcf44fe0df0a64@bwidawsk.net>
Reviewed-by: Jason Ekstrand <68c46a606457643eab92053c1c05574abb26f861@jlekstrand.net>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler