patch 9.0.0331: cannot use items() on a string

Problem:    Cannot use items() on a string.
Solution:   Make items() work on a string. (closes #11016)

src/version.c

@@ -707,6 +707,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    331,
 /**/
     330,
 /**/