Merge r579991, r580502, r584842 from trunk:

Add "DefaultType None" option
PR 13986 and PR 16139


Document "DefaultType None" option (PR 13986)


Improve documentation of "DefaultType None"

Submitted by: niq
Reviewed by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@589616 13f79535-47bb-0310-9956-ffa450edef68