mesa: if AllocStorage doesn't choose a format, report FRAMEBUFFER_UNSUPPORTED

This allows drivers not to do any allocation in AllocStorage if the storage
cannot be allocated because of an unsupported internalformat + samples combo.

The little ugliness is that AllocStorage is expected to return TRUE in this
case.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
1 file changed