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/editors/interface/interface_intern.h

@@ -290,6 +290,8 @@ struct uiBlock {
 	int tooltipdisabled;		// to avoid tooltip after click
 
 	int active;					// to keep blocks while drawing and free them afterwards
+
+	void *evil_C;				// XXX hack for dynamic operator enums
 };
 
 typedef struct uiSafetyRct {