Convert x11-toolkits/libxfce4gui and all dependent ports to USES=libtool.
And USES=tar:bzip2 here and there.
deskutils/xfce4-notification-daemon:
- Don't patch Makefile.am.
- Link with -lgmodule-2.0 explicitly now that libgtk-x11-2.0.la does not
imply it.
x11/xfce4-wmdock-plugin:
- Make it fetchable.