Invert the meaning of the -S option and document it.

This option was added recently as part of the enhanced watchdog work
done by alfred@. It is safe and more useful to call syslog(3) by default
if we're timing the watchdog command.

Additionally fix some style bugs and don't explicitly carp to stderr
unless -S is set - otherwise we'll carp to stderr twice, since syslog(3)
already does this.
Merge branch '20130326-watchdogd-syslog-cleanup' into markj-develop