[HB] Use face_t directly instead of ot_layout_t

src/hb-ot-layout-gdef-private.hh

diff --git a/src/hb-ot-layout-gdef-private.hh b/src/hb-ot-layout-gdef-private.hh
index b890099..560a07e 100644
--- a/src/hb-ot-layout-gdef-private.hh
+++ b/src/hb-ot-layout-gdef-private.hh
@@ -29,6 +29,8 @@
 
 #include "hb-ot-layout-common-private.hh"
 
+#include "hb-font-private.h"
+
 
 struct GlyphClassDef : ClassDef
 {