patch 8.1.0414: v:option_old is cleared when using :set in OptionSet autocmd

Problem:    v:option_old and v:option_new are cleared when using :set in
            OptionSet autocmd. (Gary Johnson)
Solution:   Don't trigger OptionSet recursively.

src/version.c

@@ -794,6 +794,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    414,
 /**/
     413,
 /**/