patch 9.0.1540: reverse() on string doesn't work in compiled function

Problem:    reverse() on string doesn't work in compiled function.
Solution:   Accept string in argument type check. (Yegappan Lakshmanan,
            closes #12377)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1540,
 /**/
     1539,
 /**/