mpm_event: move lingering close "sucker" from the listener to worker(s).

This was the last non-constant time action performed by the listener thread.

It's now handled by the worker thread directly after entering lingering close,
which should directly address the cases when the socket is already closed
remotely at that time, hence avoid more scheduling (it may be the common case
for some scenarios).

And it's only if the above would need blocking (i.e. more data to suck) that
the socket is added to the pollset for the listener to re-schedule a worker
later when ready. If no worker is available at that time then the socket is
forcibly closed (similarly to what's done for keepalive connections in this
case).

Also, since process_lingering_close() is now called by a worker thread and
with almost no depth in the call stack, we can grow the size of the "suck"
buffer from 2K to 32K to potentially call recv() up to sixteen times less.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1823047 13f79535-47bb-0310-9956-ffa450edef68