patch 8.1.1311: aborting an autocmd with an exception is not tested

Problem:    Aborting an autocmd with an exception is not tested.
Solution:   Add a test.  Also shows how to abort a command by throwing an
            exception.

src/version.c

@@ -767,6 +767,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1311,
 /**/
     1310,
 /**/