Fix streaming output from an nph- CGI script. CGI:IRC now

works.

core output filter needs to detect when no more data is available from
a pipe for a while so that it can flush what is already there

normally, content-length filter handles this but for nph- script
we don't have content-length filter in place

PR:             8482


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@97301 13f79535-47bb-0310-9956-ffa450edef68