Leave a warning to the sysop if (s)he didn't yet
enable the /tmp cleanup code.
Made `core' in the cleanup template look `*.core'.
Replace `df -k' by `df -k -t local', since the stats
for kernfs, procfs etc. are not of much interest, and
the inclusion of nfs systems might hang the machine (nor is it a
`disk' statistic as the headline's telling).
weekly:
Modified the locate.updatedb part to work even if there's no
database yet; report errors other than `Permission denied' instead
of silently ignoring all of them.
Added functionality to rebuild the whatis database once a week.
