patch 9.0.0318: clearing screen causes flicker

Problem:    Clearing screen causes flicker.
Solution:   Do not clear but redraw in more cases.  Add () to "wait_return".

src/ex_getln.c

@@ -1666,7 +1666,7 @@ getcmdline_int(
     if (!cmd_silent)
     {
 	i = msg_scrolled;
-	msg_scrolled = 0;		// avoid wait_return message
+	msg_scrolled = 0;		// avoid wait_return() message
 	gotocmdline(TRUE);
 	msg_scrolled += i;
 	redrawcmdprompt();		// draw prompt or indent