* doc/dbus-specification.sgml: work on the specification

	* dbus/dbus-message.c (_dbus_message_loader_return_buffer): check
	the protocol version of the message.

	* dbus/dbus-protocol.h: drop special _REPLY names, the spec
	no longer specifies that.
	(DBUS_SERVICE_REPLY_SERVICE_EXISTS): fix flags (1/2/4/8 not
	1/2/3/4)

	* dbus/dbus-marshal.c (_dbus_marshal_get_arg_end_pos): add missing
	"break" for DBUS_TYPE_NIL, remove @todo