patch 9.0.0311: test for hit-Enter prompt fails

Problem:    Test for hit-Enter prompt fails.
Solution:   Only reset cmdline_row when 'cmdheight' is zero.
diff --git a/src/version.c b/src/version.c
index d8a6862..e6ecb97 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    311,
+/**/
     310,
 /**/
     309,