Обсуждение: pgsql: Doc: updates for v12 release notes.

Doc: updates for v12 release notes.

Remove mention of ECPG's DECLARE STATEMENT, since that was reverted
yesterday.  Rewrite some other entries per suggestions from Peter
Eisentraut.  Make a couple of desultory wording and markup adjustments.

Discussion: https://postgr.es/m/d4dff575-90ab-9c8c-cc6f-8c657e2de665@2ndquadrant.com

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/25f9368304e41c8837f59e94b161f07ac4c7d622

Modified Files
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doc/src/sgml/release-12.sgml | 253 ++++++++++++++++++++-----------------------
1 file changed, 119 insertions(+), 134 deletions(-)