SIIG Cyber Serial 4S and system hang

[Roy Badami]

> Although things seem to be working, I'd like to get to the bottom of
> this so that I can be confident that the machine won't freeze again in
> the future - and I have more serial applications I need to run on this
> server.

I spoke too soon.  Although things seemed to be working, SMS Server Tools 
would lose communication with the serial-attached GSM terminal after a few 
hours.

Bottom line is that it appears that for whatever reason the uart(4) driver 
can't reliably drive the SIIG CyberSerial 4S (16550-based) card.

After a bit of Googling I followed the advice of others who have had 
problems with the uart(4) driver not working well with their hardware, and 
built a kernel without it.  In that case, puc(4) will drive the card with 
the sio(4) driver instead.

Running in this configuration the system has been rock solid for two 
weeks, with all devices (thermometer, GSM terminal and two UPSs) attached 
to the SIIG card.

I'll raise a PR.

-roy