mod_status: Cumulate CPU time of exited child

processes in the "cu" and "cs" values.
Add CPU time of the parent process to the
"c" and "s" values.

Backport of r1837595 from trunk.

Submitted by: rjung
Reviewed by: rjung, jim, ylavic


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1839531 13f79535-47bb-0310-9956-ffa450edef68