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>

src/intel/common/gen_debug.h

@@ -82,6 +82,7 @@ extern uint64_t INTEL_DEBUG;
 #define DEBUG_NO_RBC              (1ull << 38)
 #define DEBUG_NO_HIZ              (1ull << 39)
 #define DEBUG_COLOR               (1ull << 40)
+#define DEBUG_REEMIT              (1ull << 41)
 
 #ifdef HAVE_ANDROID_PLATFORM
 #define LOG_TAG "INTEL-MESA"