Continue making httpd.conf even smaller.

* httpd.conf.in: Remove PidFile; move a bunch of configuration options that
  are backed by equivalent run-time defaults to...
* extra/httpd-default.conf.in (added): ...here.
* extra/httpd-mpm.conf.in: Move PidFile example here.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/simple-conf@160063 13f79535-47bb-0310-9956-ffa450edef68