Add an experiment to disable lpf on tile boundaries

This commit adds a new experiment to allow disabling of loop filtering
on tile boundaries. It is implemented by adding a syntax field
"loopfilter_across_tiles_enabled" into the uncompressed frame header. 
If it is set to 0, decoder and encoder will disables loop filtering for
block edges that are also tile boundaries.

Change-Id: Ib80bfd82d49c74f1ba46ae18ceedb30704ac8aa5
diff --git a/av1/common/blockd.h b/av1/common/blockd.h
index 9fd5510..859986a 100644
--- a/av1/common/blockd.h
+++ b/av1/common/blockd.h
@@ -350,6 +350,9 @@
   int num_proj_ref[2];
   WarpedMotionParams wm_params[2];
 #endif  // CONFIG_WARPED_MOTION
+#if CONFIG_DEBLOCKING_ACROSS_TILES
+  TILE_BOUNDARY_TYPE tile_boundary_info;
+#endif  // CONFIG_DEBLOCKING_ACROSS_TILES
 } MB_MODE_INFO;
 
 typedef struct MODE_INFO {