Ability to listen on two unix sockets

Hi,

before I ask the main question, just a little background for one issue 
we're currently having in Fedora 17:

PrivateTmp is a systemd's feature, which allows to have private /tmp 
directory for services, which in turn means that such services aren't 
able to access systems's /tmp directory. It's been enabled by some 
services already, including Apache, while PostgreSQL uses system's /tmp 
directory, where its unix socket is located. Naturally, it resulted in a 
state, where Apache or other services with PrivateTmp enabled are not 
able to communicate with PostgreSQL using the socket.

Since we don't want just to move socket for compatibility reasons, I'm 
going to prepare a draft patch to allow PostgreSQL to use a second unix 
socket at a time. A question I'd like to ask now is: Do we need a new 
configuration variable for this or it's enough to have the location 
hard-coded? What are your opinions?

Regards,
Honza