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".
diff --git a/src/message.c b/src/message.c
index 5c5e378..ebf1985 100644
--- a/src/message.c
+++ b/src/message.c
@@ -94,7 +94,7 @@
 /*
  * msg(s) - displays the string 's' on the status line
  * When terminal not initialized (yet) mch_errmsg(..) is used.
- * return TRUE if wait_return not called
+ * return TRUE if wait_return() not called
  */
     int
 msg(char *s)
@@ -631,7 +631,7 @@
  * Rings the bell, if appropriate, and calls message() to do the real work
  * When terminal not initialized (yet) mch_errmsg(..) is used.
  *
- * Return TRUE if wait_return not called.
+ * Return TRUE if wait_return() not called.
  * Note: caller must check 'emsg_not_now()' before calling this.
  */
     static int
@@ -758,7 +758,7 @@
     attr = HL_ATTR(HLF_E);	    // set highlight mode for error messages
     if (msg_scrolled != 0)
 	need_wait_return = TRUE;    // needed in case emsg() is called after
-				    // wait_return has reset need_wait_return
+				    // wait_return() has reset need_wait_return
 				    // and a redraw is expected because
 				    // msg_scrolled is non-zero
 
@@ -2456,7 +2456,7 @@
 	    {
 #endif
 		inc_msg_scrolled();
-		need_wait_return = TRUE; // may need wait_return in main()
+		need_wait_return = TRUE; // may need wait_return() in main()
 		redraw_cmdline = TRUE;
 		if (cmdline_row > 0 && !exmode_active)
 		    --cmdline_row;
@@ -3716,8 +3716,8 @@
 
 /*
  * end putting a message on the screen
- * call wait_return if the message does not fit in the available space
- * return TRUE if wait_return not called.
+ * call wait_return() if the message does not fit in the available space
+ * return TRUE if wait_return() not called.
  */
     int
 msg_end(void)