pgsql: Adjust some glossary terms

Adjust some glossary terms

Mostly in response to Jürgen Purtz critique of previous definitions,
though I added many other changes.

Author: Álvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Jürgen Purtz <juergen@purtz.de>
Reviewed-by: Justin Pryzby <pryzby@telsasoft.com>
Reviewed-by: Erik Rijkers <er@xs4all.nl>
Discussion: https://postgr.es/m/c1e06008-2132-30f4-9b38-877e8683d418@purtz.de

Branch
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REL_13_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/91a890bd7fef1cd8bfe3c8832eea114290f16b02

Modified Files
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doc/src/sgml/glossary.sgml | 399 +++++++++++++++++++++++++++------------------
1 file changed, 240 insertions(+), 159 deletions(-)