pgsql: Fix two bugs in tsquery @> operator.

Fix two bugs in tsquery @> operator.

1. The comparison for matching terms used only the CRC to decide if there's
a match. Two different terms with the same CRC gave a match.

2. It assumed that if the second operand has more terms than the first, it's
never a match. That assumption is bogus, because there can be duplicate
terms in either operand.

Rewrite the implementation in a way that doesn't have those bugs.

Backpatch to all supported versions.

Branch
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REL9_2_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/604d94d4cacc787bfa41452785a2927c24829fc5

Modified Files
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src/backend/utils/adt/tsquery_op.c |  131 +++++++++++++++++++++++++-----------
1 file changed, 90 insertions(+), 41 deletions(-)