Обсуждение: pgsql: Doc: back-patch documentation about limitations of CHECK constra

Doc: back-patch documentation about limitations of CHECK constraints.

Back-patch commits 36d442a25 and 1f66c657f into all supported
branches.  I'd considered doing this when putting in the latter
commit, but failed to pull the trigger.  Now that we've had an
actual field complaint about the lack of such docs, let's do it.

Per bug #16158 from Piotr Jander.  Original patches by Lætitia Avrot,
Patrick Francelle, and me.

Discussion: https://postgr.es/m/16158-7ccf2f74b3d655db@postgresql.org

Branch
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REL9_4_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3ddd8ee7167f14b8792f36f6fdfec8b57daec035

Modified Files
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doc/src/sgml/ddl.sgml               | 53 +++++++++++++++++++++++++++
doc/src/sgml/ref/alter_domain.sgml  | 26 +++++++++++---
doc/src/sgml/ref/alter_table.sgml   | 71 ++++++++++++++++++++++++-------------
doc/src/sgml/ref/create_domain.sgml | 24 +++++++++++++
doc/src/sgml/ref/create_table.sgml  |  3 +-
5 files changed, 147 insertions(+), 30 deletions(-)