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/makesrna/intern/makesrna.c

@@ -1597,7 +1597,6 @@ static void rna_generate_property(FILE *f, StructRNA *srna, const char *nest, Pr
 						DefRNA.error= 1;
 					}
 				}
-				else if(eprop->itemf);
 				else {
 					fprintf(stderr, "rna_generate_structs: %s%s.%s, enum must have items defined.\n", srna->identifier, errnest, prop->identifier);
 					DefRNA.error= 1;