Disable mod_userdir by default.

This is non-backwards-compatible.  But it shouldn't effect most people,
because almost everyone has a UserDir directive in their config
anyway.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/simple-conf@160296 13f79535-47bb-0310-9956-ffa450edef68