fix for error comparing py-struct members

if 2 pyrna structs used the same pointer they could incorrectly compare as true, this caused an error in theme saving because an item could match its parent and stop writing (to prevent recursive writing of same data).

eg:
  context.user_preferences.themes[0].user_interface.wcol_regular == context.user_preferences.themes[0].user_interface

source/blender/python/intern/bpy_rna.c

@@ -745,7 +745,7 @@ int pyrna_enum_value_from_id(EnumPropertyItem *item, const char *identifier, int
 
 static int pyrna_struct_compare(BPy_StructRNA *a, BPy_StructRNA *b)
 {
-	return (a->ptr.data == b->ptr.data) ? 0 : -1;
+	return (a->ptr.data == b->ptr.data && a->ptr.type == b->ptr.type) ? 0 : -1;
 }
 
 static int pyrna_prop_compare(BPy_PropertyRNA *a, BPy_PropertyRNA *b)