[Bug: 21.5-b28] auto-revert sets modified flag

[Stephen J. Turnbull]

Sjoerd Mullender writes:

 > When the auto-revert system (I have it set through
 > global-auto-revert-mode, set through customize) reverts a buffer, the
 > buffer is marked modified afterwards.  Obviously, the buffer is not
 > modified before it is auto-reverted (it wouldn't be reverted then),
 > but afterwards it is.

Fixed in CVS, I believe.  Hard to test fully, but it works for me and
Ville (now---and it didn't before).