glob, readdir, dir

[John W. Eaton]

I've modified glob and readdir to return cell arrays of strings
instead of character matrices.  These changes may cause some trouble
for existing code, but I think it is worth it be it seems more useful
to me to have cell arrays.

The dir function is now an M-file instead of just an alias for ls, and
if nargout > 0, it will return a structure array for Matlab
compatibility.  Since it was not possible to write

  d = dir ("some-dir")

in previous versions of Octave, I don't think this change will cause
trouble.

Unfortunately, it is quite slow for large directories, so it may have
to be rewritten in C++.

Comments?

jwe