[9fans] errstr

[Russ Cox <rsc@swtch.com>]

I think I've restored the file name-related error messages
to their original 9P2000 usefulness.  Due to a mistake on
my part two years ago, they'd broken and were always
showing the full path, even if the error happened much
earlier.  For example, if the directory "does" does not exist,
this is a bad error:

	% >does/not/exist
	does/not/exist: rc: can't open: 'does/not/exist' file does not exist
	% 

In contrast, this is a good error:

	% >does/not/exist
	does/not/exist: rc: can't open: 'does' file does not exist
	% 

There are new kernels on sources as of Saturday that
should have good error messages.  If you see any errors 
that don't show the right path:

  - check that you're running a new kernel 
    (ls -l '#c/cons' and see that the date is recent) 
  - if ramfs is involved, check that it's also new
    (ls -l /386/bin/ramfs) 

and then mail me.

Thanks.
Russ