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