RNA

* Enums can now be dynamically created in the _itemf callback,
  using RNA_enum_item(s)_add, RNA_enum_item_end. All places asking
  for enum items now need to potentially free the items.
* This callback now also gets context, this was added specifically
  for operators. This doesn't fit design well at all, needed to do
  some ugly hacks, but can't find a good solution at the moment.
* All enums must have a default list of items too, even with an
  _itemf callback, for docs and fallback in case there is no context.

* Used by MESH_OT_merge, MESH_OT_select_similar, TFM_OT_select_orientation.
* Also changes some operator properties that were enums to booleas
  (unselected, deselect), to make them consistent with other ops.

source/blender/python/intern/bpy_util.c

@@ -412,7 +412,8 @@ char *BPy_enum_as_string(EnumPropertyItem *item)
 	char *cstring;
 
 	for (e= item; item->identifier; item++) {
-		BLI_dynstr_appendf(dynstr, (e==item)?"'%s'":", '%s'", item->identifier);
+		if(item->identifier[0])
+			BLI_dynstr_appendf(dynstr, (e==item)?"'%s'":", '%s'", item->identifier);
 	}
 
 	cstring = BLI_dynstr_get_cstring(dynstr);