Use new 'python-mapnik2' package for wheezy
wheezy binary from cgi-mapserver package
Specify both squeeze and wheezy packages for mapnik
python-flup is required by tilecache.fcgi
mapserver >=6.0 needs web services to be enabled explicitly

See http://mapserver.org/MIGRATION_GUIDE.html#ogc-web-services
Merge remote-tracking branch 'origin/wheezy-changes'