* dbus/dbus-internals.c (_dbus_generate_uuid): The spec said the
	UUID had the timestamp last, but the implementation had it first;
	move it to last since I think it's a tiny bit nicer (easier to
	compare at a glance, faster to sort, less code), and will not
	cause any practical compatibility problems. Also, always convert
	the timestamp to big endian.

	* doc/dbus-specification.xml: Clean up the docs on the UUID.

	* tools/dbus-uuidgen.1: more prominently say it is not suitable
	as a replacement for regular uuidgen/RFC4122.