patch 8.2.3818: cannot filter or map characters in a string

Problem:    Cannot filter or map characters in a string.
Solution:   Make filter() and map() work on a string. (Naruhiko Nishino,
            closes #9327)

src/version.c

@@ -749,6 +749,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3818,
 /**/
     3817,
 /**/