when true the server checks whether HTTP_HOST environment variable
is the same as base_url from the config (of course without the 'http://' part
and the last slash) - if it's not the same then the server
redirects you into a new location base_url+REQUEST_URI
changed: variables env_* from Request are never null (after Request::Read())
if the server didn't set such a variable it will be pointing into an empty string "\0"
git-svn-id: svn://ttmath.org/publicrep/cmslu/trunk@465 e52654a7-88a9-db11-a3e9-0013d4bc506e