patch 7.4.801

Problem:    Test for ":diffoff" doesn't catch all potential problems.
Solution:   Add a :diffthis and a :diffoff command. (Olaf Dabrunz)

src/version.c

@@ -741,6 +741,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    801,
 /**/
     800,
 /**/