Обсуждение: pgsql: Rewrite docs for new libpq keepalive parameters.

Log Message:
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Rewrite docs for new libpq keepalive parameters.

The revised documentation makes it more clear that these are client-side
parameters, rather than server side parameters.  It also puts the main
point of each parameter first, and consolidates the conditions under which
it might be ignored in a single list at the end.

Modified Files:
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    pgsql/doc/src/sgml:
        libpq.sgml (r1.309 -> r1.310)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/libpq.sgml?r1=1.309&r2=1.310)