pgsql: Add /contrib/pg_standby: pg_standby is a production-ready

Log Message:
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Add /contrib/pg_standby:

pg_standby is a production-ready program that can be used to
create a Warm Standby server. Other configuration is required
as well, all of which is described in the main server manual.

Simon Riggs

Modified Files:
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pgsql/contrib:
Makefile (r1.70 -> r1.71)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/contrib/Makefile.diff?r1=1.70&r2=1.71)