patch 8.2.3400: ":z!" is not supported

Problem:    ":z!" is not supported.
Solution:   Make ":z!" work and add tests. (Dominique Pellé, closes #8836)
            Use display height instead of current window height.

src/version.c

@@ -755,6 +755,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    3400,
 /**/
     3399,
 /**/