[bindings] Fix hb_language_get_default() and hb_ot_tag_to_language()

Part of https://github.com/behdad/harfbuzz/issues/91

src/hb-common.cc

@@ -334,7 +334,7 @@ hb_language_to_string (hb_language_t language)
  *
  * 
  *
- * Return value: 
+ * Return value: (transfer none):
  *
  * Since: 1.0
  **/

src/hb-ot-tag.cc

@@ -870,6 +870,15 @@ hb_ot_tag_from_language (hb_language_t language)
   return HB_OT_TAG_DEFAULT_LANGUAGE;
 }
 
+/**
+ * hb_ot_tag_to_language:
+ *
+ * 
+ *
+ * Return value: (transfer none):
+ *
+ * Since: 1.0
+ **/
 hb_language_t
 hb_ot_tag_to_language (hb_tag_t tag)
 {