Rename this testgtk to gtk-demo to avoid confusion, and install it so

Rename this testgtk to gtk-demo to avoid confusion, and install it so

2000-11-12  Havoc Pennington  <hp@pobox.com>

        Rename this testgtk to gtk-demo to avoid confusion, and
	install it so people can use it as a supplement to
	the documentation.

	        * demos/gtk-demo: Moved from demos/testgtk

		* demos/testgtk: Removed

		* configure.in: make Makefile in gtk-demo

		* demos/gtk-demo/Makefile.am: Install sample source to
		datadir/gtk-demo (maybe there's a better place?), and
		rename the binary to gtk-demo

		* demos/gtk-demo/main.c (load_file): Load installed sample
		source if source isn't found in pwd.