pgsql: Teach pattern_fixed_prefix() about collations.

Teach pattern_fixed_prefix() about collations.

This is necessary, not optional, now that ILIKE and regexes are collation
aware --- else we might derive a wrong comparison constant for index
optimized pattern matches.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/3c381a55b0fa1c4ca328211e39df8e1a715129cb

Modified Files
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src/backend/optimizer/path/indxpath.c | 34 +++++----
src/backend/utils/adt/selfuncs.c | 137 +++++++++++++++++++++++----------
src/include/utils/selfuncs.h | 1 +
3 files changed, 117 insertions(+), 55 deletions(-)