Enable two OpenType features, 'Harf' and 'Buzz'

One early, before script-specific features, one late, after.  Allows font
developers to detect us and behave differently if needed.

src/hb-ot-shape.cc

@@ -132,9 +132,13 @@ hb_ot_shape_collect_features (hb_ot_shape_planner_t          *planner,
   /* Random! */
   map->enable_feature (HB_TAG ('r','a','n','d'), F_RANDOM, HB_OT_MAP_MAX_VALUE);
 
+  map->enable_feature (HB_TAG('H','a','r','f'));
+
   if (planner->shaper->collect_features)
     planner->shaper->collect_features (planner);
 
+  map->enable_feature (HB_TAG('B','u','z','z'));
+
   for (unsigned int i = 0; i < ARRAY_LENGTH (common_features); i++)
     map->add_feature (common_features[i]);