patch 9.0.0053: E1281 not tested with the old regexp engine

Problem:    E1281 not tested with the old regexp engine.
Solution:   Loop over the values of 'regexp'. (Dominique Pellé, closes #10695)

src/version.c

@@ -735,6 +735,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    53,
 /**/
     52,
 /**/