Simplify the interface to ap_reclaim_child_processes() and

ap_relieve_child_processes(): instead of requiring the MPM
to implement an otherwise-useless hook, just use a callback
function.

As I don't expect third-party MPM devs are following our day
to day progress, the API changes are considered part of
yesterday's MMN change.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1087085 13f79535-47bb-0310-9956-ffa450edef68