check-system-configuration.sh:  check for common problems

Instead of installing /etc/rsyslog.d/linuxcnc.conf,
/etc/security/limits.d/linuxcnc.conf and
/etc/udev/rules.d/50-LINUXCNC-shmdrv.rules from Makefile in RIP
builds, run the check-system-configuration.sh after 'make setuid' to
check for these configuration problems.

At the same time, add those missing files to non-RIP installs.

check-system-configuration.sh is the former check-logging.sh, renamed
and extended.

(This also fixes these files not being installed by $(FILE) and thus
world-readable, a problem with buildbot's funky 077 netmask.)
runtests script:  run with 'bash -e'

Without '-e', runtests can exit 0 when tests didn't actually run.

This was observed when the /tmp filesystem became full, and
$TMPDIR/alltests couldn't be written.

When '$?' is checked, this is handling a possible non-success exit
from the previous command.  Modify each such command so that the exit
code is collected but the command doesn't result in the script
exiting.