[GX] Hook up feature variations

Shape-plan caching is not implemented.
diff --git a/src/hb-coretext.cc b/src/hb-coretext.cc
index 507581b..e857dfa 100644
--- a/src/hb-coretext.cc
+++ b/src/hb-coretext.cc
@@ -288,7 +288,9 @@
 hb_coretext_shaper_shape_plan_data_t *
 _hb_coretext_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan HB_UNUSED,
 					     const hb_feature_t *user_features HB_UNUSED,
-					     unsigned int        num_user_features HB_UNUSED)
+					     unsigned int        num_user_features HB_UNUSED,
+					     const int          *coords HB_UNUSED,
+					     unsigned int        num_coords HB_UNUSED)
 {
   return (hb_coretext_shaper_shape_plan_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }
@@ -1280,7 +1282,9 @@
 hb_coretext_aat_shaper_shape_plan_data_t *
 _hb_coretext_aat_shaper_shape_plan_data_create (hb_shape_plan_t    *shape_plan HB_UNUSED,
 					     const hb_feature_t *user_features HB_UNUSED,
-					     unsigned int        num_user_features HB_UNUSED)
+					     unsigned int        num_user_features HB_UNUSED,
+					     const int          *coords HB_UNUSED,
+					     unsigned int        num_coords HB_UNUSED)
 {
   return (hb_coretext_aat_shaper_shape_plan_data_t *) HB_SHAPER_DATA_SUCCEEDED;
 }