[Xastir] improved error messages for interface failures?

[Jason Winningham]

Had a few problems with my APRS rig on this weekend's balloon chase.   
All have been attributed to pilot error and yet another faulty Belkin  
USB hub (which I guess could also be considered pilot error, since  
it's the third time I've been bitten by a Belkin hub, but we won't go  
there).

Xastir didn't do a lot to help me troubleshoot, though.  I goofed  
entering the device special file name for the TNC serial port, but  
all I got was "ERROR" in the interface status and the standard "error  
opening interface X: hard fail" on the tty.

Could we maybe add at least errno, or even better the message  
associated with errno, when something fails?  A popup would be nice,  
but I could certainly live with it getting to the tty.

I'm posting here first before filing a feature request in case the  
information is already there and I'm overlooking it.

-Jason
kg4wsv