*) mod_proxy_fcgi: Add the support for the mod_proxy's flushpackets parameter.

*) mod_proxy_fcgi: Add the support for the mod_proxy's flushpackets parameter.
  trunk patch: http://svn.apache.org/r1802040
               http://svn.apache.org/r1807876
               http://svn.apache.org/r1808014
               http://svn.apache.org/r1805490
               http://svn.apache.org/r1823886
  2.4.x: svn merge -c 1802040,1807876,1808014,1805490,1823886 ^/httpd/httpd/trunk .
  +1: elukey, jim, ylavic
  elukey: this patch has been requested a couple of times in the users@ mailing list,
          but from my tests in trunk the async/set-aside core features would already
          do the job without the need of this patch. I am proposing the backport
          to allow more users to migrate away from mod_fastcgi.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1825771 13f79535-47bb-0310-9956-ffa450edef68