* dbus/dbus-transport-unix.c, dbus/dbus-server-unix.c: use the
	below new interfaces and include fewer system headers.

	* dbus/dbus-sysdeps.c (_dbus_read): new function
	(_dbus_write): new function
	(_dbus_write_two): new function
	(_dbus_connect_unix_socket): new function
	(_dbus_listen_unix_socket): new function

	* dbus/dbus-message-internal.h: change interfaces to use
	DBusString