patch 9.0.1271: using sizeof() and subtract array size is tricky

Problem:    Using sizeof() and subtract array size is tricky.
Solution:   Use offsetof() instead. (closes #11926)

src/version.c

@@ -695,6 +695,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1271,
 /**/
     1270,
 /**/