Merge r1601076 from trunk:

ab: support custom HTTP method with -m argument.

PR: 56604
Submitted by: Roman Jurkov <winfinit gmail.com>
Reviewed by: ylavic, trawick, covener

(r1601680 and r1601700 not reflected in mergeinfo due to
a collision with an unrelated trunk change)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1604373 13f79535-47bb-0310-9956-ffa450edef68