search: with --zero, drop a message at the same time as the spotlight

Messages like "Search Wrapped" and "This is the only occurrence"
do not need to be shown until the next keystroke.  Dropping them
quickly gives a better fullscreen experience.

src/winio.c

@@ -221,6 +221,8 @@ void read_keys_from(WINDOW *win)
 
 			if (input == ERR) {
 				if (spotlighted || LINES == 1) {
+					if (ISSET(ZERO) && lastmessage > VACUUM)
+						wredrawln(edit, editwinrows - 1 , 1);
 					lastmessage = VACUUM;
 					spotlighted = FALSE;
 					update_line(openfile->current, openfile->current_x);