pgsql: Fix two-argument form of ts_rewrite() so it actually works for

Log Message:
-----------
Fix two-argument form of ts_rewrite() so it actually works for cases where
a later rewrite rule should change a subtree modified by an earlier one.
Per my gripe of a few days ago.

Modified Files:
--------------
    pgsql/src/backend/utils/adt:
        tsquery_rewrite.c (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tsquery_rewrite.c?r1=1.4&r2=1.5)
        tsquery_util.c (r1.4 -> r1.5)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/adt/tsquery_util.c?r1=1.4&r2=1.5)
    pgsql/src/include/tsearch:
        ts_utils.h (r1.6 -> r1.7)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/include/tsearch/ts_utils.h?r1=1.6&r2=1.7)
    pgsql/src/test/regress/expected:
        tsearch.out (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/test/regress/expected/tsearch.out?r1=1.3&r2=1.4)