Merge r1205419 from trunk:

Add ap_pass_brigade_fchk() which does a Filter CHecK on the
brigade pass.
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1205424 13f79535-47bb-0310-9956-ffa450edef68