Add Perforce submitted changelist support to post-review.

Review Request #158 — Created Oct. 1, 2007 and submitted — Latest diff uploaded


Review Board SVN (deprecated)


- Support submitted changelists in Perforce.
- Silence subversion warning message when not using subversion.
- Fix some minor bugs (improperly referenced variables).
- Verify change number is an integer and give a friendly error message.
- Support BSD style diff timestamps.
Posted pending and submitted changelists in Perforce.

Posted a normal change in subversion (this change, in fact).

Tested on FreeBSD (hence the BSD support), but have not tested on Linux.  Should not be a factor, I just don't have a Linux box handy to test on.