This small patch modifies the log's to use plog instead of pconf.

This small patch modifies the log's to use plog instead of pconf.
Basically pconf is cleared at different times from plog, and this
has the effect of leaving stderr closed when going into the next
stage of the config. This also had the effect of allowing FreeBSD
with threads to create a pipe with stderr's fd at one end, and this
resulted in problems with the signal polling and high cpu usage.

In addition, move the clearing of plog from main.c to core.c where
it seems more appropriate.

This solves the first and main problem that FreeBSD has with the
threaded MPM's.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@92769 13f79535-47bb-0310-9956-ffa450edef68