Add rh-postgresql94 to the list

Hi,

I've found that postgresql92 package is listed for RHEL/CentOS/SL/OL 6 
at http://www.postgresql.org/download/linux/redhat/, but now there is 
also rh-postgresql94 package available for both, 6 and 7 OS versions 
(also as SCL), so it may be helpful for people to know that.

Hopefully this is a good list for asking for such a change.

Honza