patch 8.2.1510: using "var" in :def function may refer to legacy script var

Problem:    Using "var" in a :def function may refer to a legacy Vim script
            variable.
Solution:   Require using "s:" to refer to a legacy Vim script variable.
            (closes #6771)

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1510,
 /**/
     1509,
 /**/