* dbus/dbus-marshal.c: (_dbus_marshal_string),
	(_dbus_demarshal_string), (_dbus_marshal_test):
	* dbus/dbus-marshal.h:
	Document these functions.

	* dbus/dbus-message.c: (dbus_message_get_name),
	(dbus_message_append_int32), (dbus_message_append_uint32),
	(dbus_message_append_double), (dbus_message_append_string),
	(dbus_message_append_byte_array):
	* dbus/dbus-message.h:
	Add functions for adding message fields of different types.

	* dbus/dbus-protocol.h:
	Add the different types.