pgsql: docs: replace 'master' with 'primary' where appropriate.

docs: replace 'master' with 'primary' where appropriate.

Also changed "in the primary" to "on the primary", and added a few
"the" before "primary".

Author: Andres Freund
Reviewed-By: David Steele
Discussion: https://postgr.es/m/20200615182235.x7lch5n6kcjq4aue@alap3.anarazel.de

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/9e101cf60612f4be4f855d7393531900c2986a55

Modified Files
--------------
doc/src/sgml/amcheck.sgml             |  2 +-
doc/src/sgml/backup.sgml              | 16 ++++-----
doc/src/sgml/config.sgml              | 42 +++++++++++-----------
doc/src/sgml/external-projects.sgml   |  2 +-
doc/src/sgml/high-availability.sgml   | 67 +++++++++++++++++------------------
doc/src/sgml/libpq.sgml               |  2 +-
doc/src/sgml/logical-replication.sgml |  4 +--
doc/src/sgml/monitoring.sgml          |  6 ++--
doc/src/sgml/mvcc.sgml                |  6 ++--
doc/src/sgml/pgstandby.sgml           |  2 +-
doc/src/sgml/protocol.sgml            |  2 +-
doc/src/sgml/ref/pg_basebackup.sgml   | 10 +++---
doc/src/sgml/ref/pg_rewind.sgml       |  4 +--
doc/src/sgml/runtime.sgml             |  4 +--
doc/src/sgml/wal.sgml                 |  4 +--
15 files changed, 86 insertions(+), 87 deletions(-)