Fix GPOS/kern interaction

Oops.  Was checking for kern feature in GSUB, not GPOS.

src/hb-ot-shape.cc

diff --git a/src/hb-ot-shape.cc b/src/hb-ot-shape.cc
index 936b01f..21e0693 100644
--- a/src/hb-ot-shape.cc
+++ b/src/hb-ot-shape.cc
@@ -61,7 +61,7 @@
   plan.kern_mask = plan.map.get_mask (kern_tag);
 
   bool kerning_requested = !!plan.kern_mask;
-  bool has_gpos_kern = plan.map.get_feature_index (0, kern_tag) != HB_OT_LAYOUT_NO_FEATURE_INDEX;
+  bool has_gpos_kern = plan.map.get_feature_index (1, kern_tag) != HB_OT_LAYOUT_NO_FEATURE_INDEX;
   bool disable_gpos = plan.shaper->gpos_tag &&
 		      plan.shaper->gpos_tag != plan.map.chosen_script[1];