Thread: pgsql: Update High Availability docs.

Log Message:
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Update High Availability docs. Clarify terms master/primary standby/slave,
move two paragraphs that apply to log shipping in general from the
"Alternative method for log shipping" section to the earlier sections.
Add varname tags where missing. Some small wording changes.

Modified Files:
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    pgsql/doc/src/sgml:
        high-availability.sgml (r1.68 -> r1.69)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/high-availability.sgml?r1=1.68&r2=1.69)