Allow mod_dav to do weak entity comparison function rather than a strong

entity comparison function.  (i.e. it will optionally strip the W/ prefix.)

PR: 14921 (kinda, but not really)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@98536 13f79535-47bb-0310-9956-ffa450edef68