TFTP driver changes

[Eric Norum]

I've got a version of the TFTP driver which allows things like:

chdir ("/TFTP/BOOTP_HOST/");  <<< Note the trailing / character !!! 
open ("foobar/bletch", 0);


which is equivalent to 
open ("/TFTP/BOOTP_HOST/foobar/bletch",0);

Thanks to all the great advice I received from Till Straumann and Chris
Johns this was a lot easier than I expected.  I'll send the updated
driver to Joel when I'm convinced this is working -- with luck tomorrow
morning.  As far as I can tell this should be completely backwards
compatible, since absolute /TFTP/xxxx paths continue to work as they did
before.

-- 
Eric Norum                                 eric.norum at usask.ca
Department of Electrical Engineering       Phone: (306) 966-5394
University of Saskatchewan                 FAX:   (306) 966-5407
Saskatoon, Canada.