improve -DONE_PROCESS handling with prefork MPM so that

      it returns from ap_mpm_run() and allows core Apache code
to run any required cleanups

this resolves problems such as semaphore leaks and
shared memory that isn't cleaned up

(some necessary re-indention to be done in a separate
commit; otherwise, this would be a difficult commit
to review)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@99533 13f79535-47bb-0310-9956-ffa450edef68