pgsql: Teach \d+ to show partitioning constraints.

Teach \d+ to show partitioning constraints.

The fact that we didn't have this in the first place is likely why
the problem fixed by f8bffe9e6d700fd34759a92e47930ce9ba7dcbd5
escaped detection.

Patch by Amit Langote, reviewed and slightly adjusted by me.

Discussion: http://postgr.es/m/CA+TgmoYWnV2GMnYLG-Czsix-E1WGAbo4D+0tx7t9NdfYBDMFsA@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/1848b73d4576e30c89ba450ad9f169774a6819bf

Modified Files
--------------
src/backend/catalog/partition.c | 29 ++++++++++
src/backend/utils/adt/ruleutils.c | 32 +++++++++++
src/bin/psql/describe.c | 37 +++++++++++--
src/include/catalog/catversion.h | 2 +-
src/include/catalog/partition.h | 1 +
src/include/catalog/pg_proc.h | 2 +
src/test/regress/expected/create_table.out | 89 +++++++++++++++++++++++++-----
src/test/regress/expected/foreign_data.out | 3 +
src/test/regress/sql/create_table.sql | 20 ++++++-
9 files changed, 193 insertions(+), 22 deletions(-)