logerr: errx with logging

logerr: errx with logging

Had a few complaints that the lastlog option was dropped.
It's now been restored, but with a new way of logging which is
the same as errx(3) as found on the BSD platforms but the output
also goes to the logging option of choice.

This allows the function to define the log priority for syslog
and there is no more need to specify %m.
In turn, this makes the code needed to write error messages
a lot shorter than before.

loginfo and logdebug have no optional x suffix because they are not
meant to record errors, unlike logerr and logwarn.