Remove the old test-display-menu scripts

tests/gdb-test-display-menu

-run # /usr/local/etc/xdg/menus/xfce-applications.menu
-bt
-quit

tests/run-test-display-menu.sh

-#!/bin/sh
-#
-# Copyright (c) 2007 Jannis Pohlmann <jannis@xfce.org>
-#
-# This program is free software; you can redistribute it and/or modify
-# it under the terms of the GNU General Public License as published by
-# the Free Software Foundation; either version 2, or (at your option)
-# any later version.
-#
-# This program is distributed in the hope that it will be useful,
-# but WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-# GNU General Public License for more details.
-#
-# You should have received a copy of the GNU General Public License
-# along with this program; if not, write to the Free Software
-# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
-# MA 02110-1301 USA.
-#
-
-GLIB_OPTIONS=`pkg-config --cflags --libs glib-2.0`
-GTK_OPTIONS=`pkg-config --cflags --libs gtk+-2.0`
-GARCON_OPTIONS=`pkg-config --cflags --libs garcon-1`
-
-gcc -o test-display-menu test-display-menu.c $GLIB_OPTIONS $GTK_OPTIONS $GARCON_OPTIONS &&
-G_DEBUG=fatal-criticals gdb ./test-display-menu -x gdb-test-display-menu