wrappers for err, errx, warn and warnx respectively when running in foreground
and call syslog functions when running in daemon mode.
Also add and use an extra log_info function for other types of information.
button events. This mode needs to be explicitly enabled at runtime, and
does nothing if not configured.
As there are now two different modes available, adjust the manpages
accordingly, describing what they do and how they work separatedly.
While here, remove a bunch of unused stuff (event syntax) from config file
parsing. This was initially added with this new mode in mind, but it has
not been used to make it a lot simpler.
jmmv