*) add activity handling: OPTIONS and MKACTIVITY

*) fix HTTP status code in MKWORKSPACE handling
*) add can_be_activity and make_activity hooks to dav_hooks_vsn


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87980 13f79535-47bb-0310-9956-ffa450edef68