merge r600645 from trunk:

 http_protocol: Escape request method in 413 error reporting.
 Determined to be not generally exploitable, but a flaw in any case.
 PR 44014

Submitted by: Victor Stinner <victor.stinner inl.fr>
Reviewed by: wrowe, rpluem, trawick


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@604425 13f79535-47bb-0310-9956-ffa450edef68