pgsql: Fix up core tsquery GIN support for new extractQuery API.

Fix up core tsquery GIN support for new extractQuery API.

No need for the empty-prefix-match kluge to force a full scan anymore.

Branch
------
master

Details
-------
http://git.postgresql.org/gitweb?p=postgresql.git;a=commitdiff;h=52fd2d65a33c9c33b29788e9df89d7716f1ec0bc

Modified Files
--------------
src/backend/utils/adt/tsginidx.c | 74 +++++++++++++++++------------------
src/backend/utils/adt/tsvector_op.c | 73 ++++++++++++++++++++++++++++-------
src/include/tsearch/ts_utils.h | 2 +-
3 files changed, 96 insertions(+), 53 deletions(-)