Add support for selecting candidates via mouseclick.

src/IBusChewingEngine-keys.c

 #ifndef IBUS_1_1
 gboolean ibus_chewing_engine_process_key_event_1_2(IBusEngine *engine,
         guint keysym_ignore,  guint  keycode,   guint  modifiers){
     if (modifiers & IBUS_RELEASE_MASK){
         /* Skip release event */
         return TRUE;
     }
     IBusChewingEngine *self=IBUS_CHEWING_ENGINE(engine);
     guint keysym=ibus_keymap_lookup_keysym (self->keymap_us,keycode,modifiers);
     return ibus_chewing_engine_process_key_event(engine, keysym, modifiers);
@@ skipping 180 matching lines @@
         }
 
     }else{
         result=FALSE;
     }
     if (!result){
         return FALSE;
     }
     return self_update(self);
 }
+
+void ibus_chewing_engine_candidate_clicked(IBusEngine *engine, guint index,
+        guint button, guint state) {
+    G_DEBUG_MSG(3,"[I3] cadidate_clicked(-, %u, %u, %u) ... proceed.", index, button, state);
+    IBusChewingEngine *self=IBUS_CHEWING_ENGINE(engine);
+    self_handle_candidate_clicked(self, index, button, state);
+}