(dbus_message_has_path): New method
        (dbus_message_has_interface): New method
        (dbus_message_has_member): New method

        * dbus/dbus/dbus-sysdeps.c (_dbus_check_dir_is_private_to_user):
        New method

        * dbus/dbus-keyring.c (_dbus_keyring_reload): Check to see that
        the keyring directory is private to the user

        * doc/TODO:
         - The convenience functions in dbus-bus.h should perhaps have
         the signatures that they would have if they were autogenerated
         stubs. e.g. the acquire service function. We should also evaluate
         which of these functions to include, in light of the fact that
         GLib/Qt native stubs will probably also exist.: Punted

         - add dbus_message_has_path(), maybe has_member/interface:
         fixed in this patch

         - in dbus-keyring.c, enforce that the keyring dir is not
         world readable/writable: Fixed in this patch