Minor

src/hb-ot-layout.cc

diff --git a/src/hb-ot-layout.cc b/src/hb-ot-layout.cc
index e93fc07..8ad36d2 100644
--- a/src/hb-ot-layout.cc
+++ b/src/hb-ot-layout.cc
@@ -1255,7 +1255,7 @@
   apply (proxy, plan, font, buffer);
 }
 
-HB_INTERNAL void
+void
 hb_ot_layout_substitute_lookup (OT::hb_ot_apply_context_t *c,
 				const OT::SubstLookup &lookup,
 				const hb_ot_layout_lookup_accelerator_t &accel)