patch 8.0.0501: on MS-Windows ":!start" does not work as expected

Problem:    On MS-Windows ":!start" does not work as expected.
Solution:   When creating a process fails try passing the argument to
            ShellExecute().  (Katsuya Hino, closes #1570)

src/version.c

@@ -764,6 +764,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    501,
 /**/
     500,
 /**/