pgsql: Add prefix operator for TEXT type.

Add prefix operator for TEXT type.

The prefix operator along with SP-GiST indexes can be used as an alternative
for LIKE 'word%' commands and it doesn't have a limitation of string/prefix
length as B-Tree has.

Bump catalog version

Author: Ildus Kurbangaliev with some editorization by me
Review by: Arthur Zakirov, Alexander Korotkov, and me
Discussion: https://www.postgresql.org/message-id/flat/20180202180327(dot)222b04b3(at)wp(dot)localdomain

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/710d90da1fd8c1d028215ecaf7402062079e99e9

Modified Files
--------------
doc/src/sgml/func.sgml | 21 +++++++++++++++
doc/src/sgml/spgist.sgml | 1 +
src/backend/access/spgist/spgtextproc.c | 43 +++++++++++++++++++++++++++---
src/backend/utils/adt/selfuncs.c | 33 +++++++++++++++++++++++
src/backend/utils/adt/varlena.c | 28 +++++++++++++++++++
src/include/access/stratnum.h | 3 ++-
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_amop.h | 1 +
src/include/catalog/pg_operator.h | 2 ++
src/include/catalog/pg_proc.h | 5 ++++
src/include/utils/selfuncs.h | 7 +++--
src/test/regress/expected/create_index.out | 38 ++++++++++++++++++++++++++
src/test/regress/expected/opr_sanity.out | 4 ++-
src/test/regress/sql/create_index.sql | 10 +++++++
14 files changed, 189 insertions(+), 9 deletions(-)