updated for version 7.3.516

Problem:    extend(o, o) may crash Vim.
Solution:   Fix crash and add test. (Thinca and Hirohito Higashi)

src/version.c

@@ -714,6 +714,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    516,
 /**/
     515,
 /**/