Py/RNA API test code to prevent crashing blender when python references freed ID's.

This uses pythons GC so its no overhead during runtime but makes removing ID's slower.

Commented definition 'USE_PYRNA_INVALIDATE_GC' for now, so no functional change.

source/blender/python/BPY_extern.h

@@ -93,6 +93,8 @@ void	BPY_DECREF(void *pyob_ptr);	/* Py_DECREF() */
 int		BPY_context_member_get(struct bContext *C, const char *member, struct bContextDataResult *result);
 void	BPY_context_set(struct bContext *C);
 
+void	BPY_id_release(struct ID *id);
+
 #ifdef __cplusplus
 }				/* extern "C" */
 #endif