patch 9.0.0310: output of :messages dissappears when cmdheight is zero

Problem:    Output of :messages dissappears when cmdheight is zero.
Solution:   Do not use the messages window for :messages.  Make Esc close the
            messages window.
diff --git a/src/version.c b/src/version.c
index c69e46c..d8a6862 100644
--- a/src/version.c
+++ b/src/version.c
@@ -708,6 +708,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    310,
+/**/
     309,
 /**/
     308,