pgsql: On CREATE TABLE, consider skipping validation of subpartitions.

On CREATE TABLE, consider skipping validation of subpartitions.

This is just like commit 14f67a8ee282ebc0de78e773fbd597f460ab4a54, but
for CREATE PARTITION rather than ATTACH PARTITION.

Jeevan Ladhe, with test case changes by me.

Discussion: http://postgr.es/m/CAOgcT0MWwG8WBw8frFMtRYHAgDD=tpt6U7WcsO_L2k0KYpm4Jg@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/6476b26115f3ef25a9cd87880e0ac5ec5f7a05f6

Modified Files
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src/backend/catalog/partition.c | 18 ++++++++++++++++++
src/test/regress/expected/alter_table.out | 12 +++++++++---
src/test/regress/sql/alter_table.sql | 11 ++++++++---
3 files changed, 35 insertions(+), 6 deletions(-)