Merge of r1861338,1862475,1862583,1862865,1863221,1863276 from trunk:
*) mod_http2: core setting "LimitRequestFieldSize" is not additionally checked on
merged header fields, just as HTTP/1.1 does. [Stefan Eissing, Michael Kaufmann]
*) mod_http2: fixed a bug that prevented proper stream cleanup when connection
throttling was in place. Stream resets by clients on streams initiated by them
are counted as possible trigger for throttling. [Stefan Eissing]
*) mod_http2/mpm_event: Fixes the behaviour when a HTTP/2 connection has nothing
more to write with streams ongoing (flow control block). The timeout waiting
for the client to send WINODW_UPDATE was incorrectly KeepAliveTimeout and not
Timeout as it should be. Fixes PR 63534. [Yann Ylavic, Stefan Eissing]