Currently we pass either a single format or no formats to the gl renderer
create and output_create functions.  We extend this to any number of
formats so we can allow fallback formats if we don't get our first pick.

Reviewed-By: Bryce Harrington <bryce@osg.samsung.com>
Reviewed-By: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Signed-off-by: Derek Foreman <derekf@osg.samsung.com>