Patch series for children process resource accounting

[Flavio Cruz]

These patches implement getrusage(RUSAGE_CHILDREN, _) and populate
child related data in times(_). This should fix the problem we have
with building the latest grep which uses times(_) to get the cpu cycles in the 
test
suite: 
https://buildd.debian.org/status/fetch.php?pkg=grep&arch=hurd-i386&ver=3.11-4&stamp=1704383469&raw=0