Merge r1780328, r1780329, r1781329, r1782164, r1782166, r1782193, r1778350, r1781329...

Merge r1780328, r1780329, r1781329, r1782164, r1782166, r1782193, r1778350, r1781329, r1782194, r1782323, r1782418, r1782419, r1782482, r1782532, r1788040 from trunk:

Adjust as needed

debugging

add ProxyFCGISetEnvIf

Logging update

Follow up to r1782164: fix typo (closing double-quote).

Remove trailing whitespace : no functional change

PR60576: php-fpm broken w/ per-dir rewrites

Attempt to dig out of well-meaning fixes for generic fcgi backends
that negatively affected some FPM configs.

Adds ProxyFCGIBackendType

add ProxyFCGISetEnvIf

trailing whitespace

Allow final admin-level fine-tuning

mod_proxy_fcgi: fix spelling in APLOG_INFO message

mod_proxy_fcgi: allow setting empty variables in ProxyFCGISetEnvIf

support unsetting vars

ProxyFCGISetEnvIf: reject invalid invocations, streamline unsets

Neither of the following makes sense:
- ProxyFCGISetEnvIf cond !VARIABLE value
- ProxyFCGISetEnvIf cond !

Error out in these cases. Also, don't execute the (unused) replacement
expression when unsetting.

drop the longhand version

Submitted by: jim, covener, jim, ylavic, jim, covener, covener, jim, jim, jchampion, jchampion, covener, jchampion, covener
Reviewed by: jim, covener, jchampion

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1788445 13f79535-47bb-0310-9956-ffa450edef68