i965: Add an INTEL_DEBUG=reemit option.

i965: Add an INTEL_DEBUG=reemit option.

Jason and I use this for debugging all the time.  Recompiling the driver
to enable it is kind of annoying.  It's a great thing to try along with
always_flush_batch=true and always_flush_cache=true to detect a class of
problems - namely, atoms listening to an insufficient set of dirty bits.

Reviewed-by: Matt Turner <mattst88@gmail.com>