add pre_htaccess hook; in conjunction with earlier dirwalk_stat
and post_perdir_config hooks, this should allow mpm-itk to be
used without patches to httpd core



Replace pre_htaccess hook with more flexible open_htaccess hook

Submitted by: trawick, sf
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1507680 13f79535-47bb-0310-9956-ffa450edef68