changing the /tmp/ lock file?

[Ben <bench@xxxxxxxxxxxxxxx>]

I'm trying to impliment an automatic failover system, and am running into 
the problem that when I try to start multiple postgres clusters on the 
same box, postgres will not start if /tmp/.s.PGSQL.5432.lock exists. Can I 
change the file it's looking for via an option? Nothing seemed obvious 
from a quick review of the docs, short of (presumably) changing the port 
number, which I don't want to do.