[otlayout] Add HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED

Currently unused.

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

@@ -618,10 +618,11 @@ struct hb_apply_context_t
   inline void _set_glyph_props (hb_codepoint_t glyph_index,
 			  unsigned int class_guess = 0) const
   {
+    unsigned int add_in = HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED;
     if (likely (has_glyph_classes))
-      _hb_glyph_info_set_glyph_props (&buffer->cur(), gdef.get_glyph_props (glyph_index));
+      _hb_glyph_info_set_glyph_props (&buffer->cur(), add_in | gdef.get_glyph_props (glyph_index));
     else if (class_guess)
-      _hb_glyph_info_set_glyph_props (&buffer->cur(), class_guess);
+      _hb_glyph_info_set_glyph_props (&buffer->cur(), add_in| class_guess);
   }
 
   inline void replace_glyph (hb_codepoint_t glyph_index) const

src/hb-ot-layout-private.hh

@@ -42,13 +42,15 @@
  * GDEF
  */
 
-typedef enum {
-  /* One bit available here...          = 0x01u */
-
+typedef enum
+{
   /* The following three match LookupFlags::Ignore* numbers. */
   HB_OT_LAYOUT_GLYPH_PROPS_BASE_GLYPH	= 0x02u,
   HB_OT_LAYOUT_GLYPH_PROPS_LIGATURE	= 0x04u,
-  HB_OT_LAYOUT_GLYPH_PROPS_MARK		= 0x08u
+  HB_OT_LAYOUT_GLYPH_PROPS_MARK		= 0x08u,
+
+  /* The following are used internally; not derived from GDEF. */
+  HB_OT_LAYOUT_GLYPH_PROPS_SUBSTITUTED	= 0x10u
 
 } hb_ot_layout_glyph_class_mask_t;