Make post-review work on machine configured in non english locale

Review Request #419 — Created June 22, 2008 and submitted

Review Board SVN (deprecated)
The client side "post-review" script does not work when used on a machine configured as a non English locale. This is due to the fact that the tool parses the output of the subversion commands which is not necessarily written in English. This patch makes sure the subversion command is called with the proper locale. This patch affect only subversion but it is possible that other revision control tools also need it.
Tested on a machine with locale "en_US.UTF-8" and a machine with locale "es_ES.UTF-8".
  1. Looks good.  Committed as r1390.