I've committed the Squid-related changes to HEAD.
To activate Squid purging, adjust these settings in LocalSettings.php:
# Squid-related settings
#
# Enable/disable Squid
$wgUseSquid = true;
# Internal server name as known to Squid, if different
# $wgInternalServer = 'http://yourinternal.tld.:8000';
# A list of proxy servers (ips if possible) to purge on changes
# don't specify ports here (80 is default)
$wgSquidServers = array('127.0.0.1');
More details about the changes at
http://wiki.aulinx.de/.
--
Gabriel Wicke