mod_dav: Note an API issue with the dav_hooks_repository.deliver(), dav_hooks_vsn.deliver_report() and dav_hooks_vsn.merge() hook definitions. * modules/dav/main/mod_dav.h (dav_hooks_repository.deliver, dav_hooks_vsn.deliver_report, dav_hooks_vsn.merge): Add notes about the API issue.