* configure.in: Check for getpgid.

* include/mpm_common.h (ap_mpm_safe_kill): New prototype.

* server/mpm_common.c (reclaim_one_pid): Ensure pid validity before
calling apr_proc_wait().
(ap_mpm_safe_kill): New function.

* server/mpm/prefork/prefork.c, server/mpm/worker/worker.c,
server/mpm/experimental/event/event.c: Use ap_mpm_safe_kill() on pids
from the scoreboard, throughout.

* include/ap_mmn.h: Minor bump.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@551843 13f79535-47bb-0310-9956-ffa450edef68