[layout] Rename API:

-hb_ot_layout_get_optical_bound()
+hb_ot_layout_lookup_get_optical_bound()
diff --git a/src/hb-config.hh b/src/hb-config.hh
index dbe0cb8..d56617f 100644
--- a/src/hb-config.hh
+++ b/src/hb-config.hh
@@ -71,7 +71,7 @@
 #define HB_NO_LANGUAGE_PRIVATE_SUBTAG
 #define HB_NO_LAYOUT_FEATURE_PARAMS
 #define HB_NO_LAYOUT_COLLECT_GLYPHS
-#define HB_NO_LAYOUT_RARELY_UNUSED
+#define HB_NO_LAYOUT_RARELY_USED
 #define HB_NO_LAYOUT_UNUSED
 #define HB_NO_MATH
 #define HB_NO_META