pgsql: Document that pgpool can be used with master/slave servers to

Log Message:
-----------
Document that pgpool can be used with master/slave servers to avoid
problems with non-deterministic functions.

Modified Files:
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pgsql/doc/src/sgml:
high-availability.sgml (r1.62 -> r1.63)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/high-availability.sgml?r1=1.62&r2=1.63)