pgsql: Be a little more careful with the shift computations in QT2QTN

Log Message:
-----------
Be a little more careful with the shift computations in QT2QTN and
makeTSQuerySign.  The first of these is a live bug, on some platforms,
as per bug #5590 from John Regehr.  However the consequences seem limited
because of the relatively narrow scope of use of QTNode.sign.  The shift in
makeTSQuerySign is actually safe because TSQS_SIGLEN is unsigned, but it
seems like a good idea to insert an explicit cast rather than depend on that.

Modified Files:
--------------
    pgsql/src/backend/utils/adt:
        tsquery_op.c (r1.9 -> r1.10)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tsquery_op.c?r1=1.9&r2=1.10)
        tsquery_util.c (r1.14 -> r1.15)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tsquery_util.c?r1=1.14&r2=1.15)