patch 9.0.0321: cannot use the message popup window directly

Problem:    Cannot use the message popup window directly.
Solution:   Add ":echowindow".
diff --git a/src/ex_getln.c b/src/ex_getln.c
index 2454be7..25073a8 100644
--- a/src/ex_getln.c
+++ b/src/ex_getln.c
@@ -3872,6 +3872,8 @@
     void
 redrawcmd(void)
 {
+    int save_in_echowindow = in_echowindow;
+
     if (cmd_silent)
 	return;
 
@@ -3883,6 +3885,9 @@
 	return;
     }
 
+    // Do not put this in the message window.
+    in_echowindow = FALSE;
+
     sb_text_restart_cmdline();
     msg_start();
     redrawcmdprompt();
@@ -3906,6 +3911,8 @@
     // Typing ':' at the more prompt may set skip_redraw.  We don't want this
     // in cmdline mode
     skip_redraw = FALSE;
+
+    in_echowindow = save_in_echowindow;
 }
 
     void