Merge r1803420, r1803454, r1804090 from trunk:

mod_http2: version bump, partial fix for stream response getting stuck, see https://github.com/icing/mod_h2/issues/143

mod_http2: signalling produce IO before waiting on beam buffer to drain.

mod_http2: non-dev version for backport

Submitted by: icing
Reviewed/backported by: icing, steffenal, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1807771 13f79535-47bb-0310-9956-ffa450edef68