pgsql: Fix bugs in contrib/pg_trgm's LIKE pattern analysis code.

Fix bugs in contrib/pg_trgm's LIKE pattern analysis code.

Extraction of trigrams did not process LIKE escape sequences properly,
leading to possible misidentification of trigrams near escapes, resulting
in incorrect index search results.

Fujii Masao

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/874d97c2a8211cf7daaa70ee531037e69a18f4ba

Modified Files
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contrib/pg_trgm/expected/pg_trgm.out |   12 +++++++++
contrib/pg_trgm/sql/pg_trgm.sql      |    2 +
contrib/pg_trgm/trgm_op.c            |   44 +++++++++++++++++++--------------
3 files changed, 39 insertions(+), 19 deletions(-)