{
    Oid             relId;
    Oid             dbId;
    union
    {
        BlockNumber     blkno;
        TransactionId   xid;
    }               objId;
>
> Added:
>    /*
>     * offnum should be part of objId.tupleId above, but would increase
>     * sizeof(LOCKTAG) and so moved here; currently used by userlocks only.
>     */
>    OffsetNumber    offnum;
    uint16          lockmethod;     /* needed by userlocks */
} LOCKTAG;

gmake clean required...
User locks are ready for 6.5 release...