Fix missing xscale in rtl graphite unpacking (#541)

* Fix missing xscale in rtl graphite unpacking

* Oops didn't need to mess with yscale
diff --git a/src/hb-graphite2.cc b/src/hb-graphite2.cc
index 9e0761e..bc247c6 100644
--- a/src/hb-graphite2.cc
+++ b/src/hb-graphite2.cc
@@ -389,7 +389,7 @@
   }
   else
   {
-    curradvx = gr_seg_advance_X(seg);
+    curradvx = gr_seg_advance_X(seg) * xscale;
     for (is = gr_seg_first_slot (seg); is; pPos++, info++, is = gr_slot_next_in_segment (is))
     {
       if (info->cluster != currclus)