SYNOPSIS
        string get_bb_uid(void)

DESCRIPTION
        Is called to get the ``backbone id''. Objects whose creator is
        the backbone id are ``trusted'', and will automagically get
        the uid and euid of the object that caused to load or clone
        them.

        The backbone id is also temporary given to objects while being
        called via process_string().

        If strict-euids, this function must exist and return a string.

HISTORY
        Since 3.2.1, get_bb_uid() is needed just for process_string()
        if no this_object() is present.

SEE ALSO
        uids(C), creator_file(M), creator(E), get_master_uid(M)
