pgsql: Doc: improve documentation about inheritance.

Doc: improve documentation about inheritance.

Clarify documentation about inheritance of check constraints, in
particular mentioning the NO INHERIT option, which didn't exist when
this text was written.

Document that in an inherited query, the applicable row security policies
are those of the explicitly-named table, not its children. This is the
intended behavior (per off-list discussion with Stephen Frost), and there
are regression tests for it, but it wasn't documented anywhere user-facing
as far as I could find.

Do a bit of wordsmithing on the description of inherited access-privilege
checks.

Back-patch to 9.5 where RLS was added.

Branch
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REL9_6_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/fab220b415700ac29637465e96f6745ec6e1cdb6

Modified Files
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doc/src/sgml/ddl.sgml | 32 +++++++++++++++++++++-----------
1 file changed, 21 insertions(+), 11 deletions(-)