Merge r1736463,r1737006,r1737021,r1737102,r1737125,r1737254 from trunk:

mod_http2: backport of version 1.4.6


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1737255 13f79535-47bb-0310-9956-ffa450edef68