bug#2833: 23.0.92; Bug in Directory Variables

[Chong Yidong <cyd@stupidchicken.com>]

> I think there's a bug in directory variables code, that is, changing
> the directory variables would require a restart of Emacs for them to
> take effect.

Tom, could you please take a shot at implementing this?  It may be too
late in the release to put this in 23.1 (depending on how complicated
the change turns out to be), but this problem definitely needs fixing at
some point.

I guess this is what the following comment in files.el is referring to:

(defun dir-locals-read-from-file (file)
  "Load a variables FILE and register a new class and instance.
FILE is the name of the file holding the variables to apply.
The new class name is the same as the directory in which FILE
is found.  Returns the new class name."
  (with-temp-buffer
    ;; We should probably store the modtime of FILE and then
    ;; reload it whenever it changes.
    (insert-file-contents file)