WHOA!  Fix the collatteral damage I caused by removing provider.

  mod_dav is also retrofitted for the generic ap_provider API.  Restore
  it to its 2.1 state for mod_dav (and of course, if someone wants to
  backport the aaa changes without the module names overhaul, they will
  need this API.)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@97693 13f79535-47bb-0310-9956-ffa450edef68