display: add a wnoutrefresh() call for NetBSD, to force a cursor update

With NetBSD curses, when only the cursor is moved (without writing any
text), then a call of wnoutrefresh() is needed to make doupdate() move
the cursor.  Ncurses does not need this.

This addresses https://savannah.gnu.org/patch/?10438.

src/winio.c

@@ -2534,6 +2534,10 @@ void place_the_cursor(void)
 		statusline(ALERT, "Misplaced cursor -- please report a bug");
 #endif
 
+#ifdef _CURSES_H_
+	wnoutrefresh(midwin);  /* Only needed for NetBSD curses. */
+#endif
+
 	openfile->current_y = row;
 }