stat fail

[Lars Hansen <larsh@math.ku.dk>]

When I mount a SMB file system on directory foo, unplug the network and 
then call the C function stat (or lstat) on foo, the function returns -1 
and sets errno to 5 (Input/output error). This is on a GNU/Linux system.

The results for Emacs are (among other?):
1. file-attributes may return nil although the file exists.
2. directory-files-and-attributes may return names with no attributes.
3. file-exists-p may return nil although the file exists.

I don't know if the behavior of stat is a bug or not, but even if it is, 
maybe Emacs ought to be able to handle stat failing on an existing file. 
Cases 1 and 2 may be fixed by a doc change, and problem 3 may be fixed 
by using the C function access rather than stat.