Merge r1747946 from trunk:

mod_dav: Add dav_get_provider_name() function to obtain the name
of the provider from mod_dav.

Submitted by: minfrin
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1748215 13f79535-47bb-0310-9956-ffa450edef68