icing in httpd

* mod_md: manual updates and challenge description

Merge of r1866119 from trunk:

cmake for mod_md: interim fix by bill.

Improvement to mod_md cmake support. thanks to bill.

Merge of r1864693,1864695,1864703 from trunk;

*) mod_proxy: Improve XSRF/XSS protection. [Joe Orton]

update after backport
Merged /httpd/httpd/trunk:r1864428 from trunk

*) mod_ssl: reverting a 2.4.40 change where a superfluous SSLCertificateChainFile configuration

Merged /httpd/httpd/trunk:r1864435,1864438,1864450-1864451,1864464 from trunk:

*) modules/filters: PR 63633: Fix broken compilation when using old GCC (<4.2.x).

vote and promote
proposing backport of r1864428

*) mod_ssl: reverting a 2.4.40 change where a superfluous SSLCertificateChainFile configuration

for a domain managed by mod_md caused a startup error. This happened when mod_md installed

its fallback certificate, before it got the first real certificate from Lets Encrypt.

Merged /httpd/httpd/trunk:r1864425

* mod_md: assigning APLOGNO(), silencing compiler warnings

* mod_md: fix compiler warnings

Merge of r1864192 from trunk:

*) core, rewrite: Set PCRE_DOTALL by default

adapting expectation to changed url reporting in error docs
Merge of r1863635 from trunk:

*) md_crypt: Wrap get_ct_scts_nid(void) definition to avoid unused function error

when building in maintainer mode. [jim]

update after backport
Merge of r1864191 from trunk:

*) core, proxy: remove request URL and headers from error docs

[Eric Covener]

Merged /httpd/httpd/trunk:r1864153

Fix unnecessary redefinition of AP_ENABLE_EXCEPTION_HOOK. [Eric Covener]

merge information from h2 backport
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]

Merge r1856829 from trunk:

*) mod_proxy: Load balancer byrequests required when bytraffic chosen

PR 62372

vote and promote

update after backport
Merging r1853560 from trunk:

*) mod_proxy_hcheck: Create the configure for mod_proxy_hcheck when used in BalancerMember.

PR 60757

vote and promote

update after backport