Log Message:
-----------
Add mention of pl/proxy toolset to docs.
Modified Files:
--------------
pgsql/doc/src/sgml:
high-availability.sgml (r1.19 -> r1.20)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/high-availability.sgml?r1=1.19&r2=1.20)