Thread: pgsql: Move pl/proxy into Multi-server parallel query execution

Log Message:
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Move pl/proxy into Multi-server parallel query execution documentation
section.

Modified Files:
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    pgsql/doc/src/sgml:
        high-availability.sgml (r1.21 -> r1.22)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/high-availability.sgml?r1=1.21&r2=1.22)