add ops & methods to hb_bimap_t making it more like hb_map_t
moved has () to hb_bimap_t from hb_inc_bimap_t
moved identity () to hb_inc_bimap_t
removed forward()

src/hb-subset-cff-common.cc

diff --git a/src/hb-subset-cff-common.cc b/src/hb-subset-cff-common.cc
index 1da5c4a..b71ac57 100644
--- a/src/hb-subset-cff-common.cc
+++ b/src/hb-subset-cff-common.cc
@@ -114,7 +114,7 @@
 
     /* update each font dict index stored as "code" in fdselect_ranges */
     for (unsigned int i = 0; i < fdselect_ranges.length; i++)
-      fdselect_ranges[i].code = fdmap.forward (fdselect_ranges[i].code);
+      fdselect_ranges[i].code = fdmap[fdselect_ranges[i].code];
   }
 
   /* determine which FDSelect format is most compact */