patch 9.1.0113: duplicate code when cleaning undo stack

Problem:  duplicate code when cleaning undo stack
Solution: refactor undo cleanup into a single public function

related: #13928

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    113,
 /**/
     112,
 /**/