pgsql: Mention pg_backend_pid() in the system information section in

Log Message:
-----------
Mention pg_backend_pid() in the system information section in addition
to the monitoring section.

Jim Nasby

Modified Files:
--------------
pgsql/doc/src/sgml:
func.sgml (r1.428 -> r1.429)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml?r1=1.428&r2=1.429)
monitoring.sgml (r1.56 -> r1.57)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/monitoring.sgml?r1=1.56&r2=1.57)