Default timezone changes in 9.1

We recently began upgrading our clients' servers from 9.0 -> 9.2. After a
few deployments and a little digging we noticed that 9.0 -> 9.1 broke the
use of no timezone set within postgresql.conf. That is, not setting the
option was now defaulting to GMT instead of the system timezone.
Unfortunately, this put quite a damper on our "one configuration file to
rule them all" setup across servers located throughout various time zones.

I obtained the commit ca4af308c32d03db5fbacb54d6e583ceb904f268 from the git
repository and have reversed it against 9.2. Though it didn't apply as
smoothly as initially hoped; applying a few of the failed hunks manually
allowed me to successfully compile 9.2.1 with these changes reversed.

After some (light) testing, the previous functionality of the system
choosing the timezone at runtime seems to be functional again.

I found this functionality invaluable and figured I'd get the patch (
http://pastebin.com/5AyaX2RF) posted in case anyone else ever needs this
functionality back. It works against 9.2.1; no guarantees on future
releases of course and YMMV.

T.J.