make sure this is defined, so that mpm_common.c compiles with the right

   values, functions, whatever. specifically, ap_reclaim_child_processes()
   was not getting compiled into mpm_common.
this appears to keep mpmt_pthread running properly. dunno whether a similar
   issue exists for prefork or dexter. (until all are torched)


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85815 13f79535-47bb-0310-9956-ffa450edef68