mod_rewrite shouldn't make any assumptions on which characters a username can

contain because a lot of Unix derivates allow more then [a-zA-Z0-9]. We now
treat anything between ^/~ and  the next slash or end of URL as the username
because this does not hurt us. We always expand only after we have
successfully resolved the cut out name via /etc/passwd.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80302 13f79535-47bb-0310-9956-ffa450edef68