pgsql: Add width_bucket(anyelement, anyarray).

Add width_bucket(anyelement, anyarray).

This provides a convenient method of classifying input values into buckets
that are not necessarily equal-width.  It works on any sortable data type.

The choice of function name is a bit debatable, perhaps, but showing that
there's a relationship to the SQL standard's width_bucket() function seems
more attractive than the other proposals.

Petr Jelinek, reviewed by Pavel Stehule

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/e80252d424278abf65b624669c8e6b3fe8587cac

Modified Files
--------------
doc/src/sgml/func.sgml               |   33 +++--
src/backend/utils/adt/arrayfuncs.c   |  243 ++++++++++++++++++++++++++++++++++
src/include/catalog/catversion.h     |    2 +-
src/include/catalog/pg_proc.h        |    6 +-
src/include/utils/array.h            |    1 +
src/test/regress/expected/arrays.out |  123 +++++++++++++++++
src/test/regress/sql/arrays.sql      |   62 +++++++++
7 files changed, 458 insertions(+), 12 deletions(-)