File watch support in autorevert.el

[Michael Albinus]

Hi,

As a proof of concept, I have installed a patch in autorevert.el
implementing file watches.  This shall work for `auto-revert-mode' and
`global-auto-revert-mode' for buffers visiting files.
`auto-revert-tail-mode' is not supported (yet).

The implementation uses `inotify-*-watch' functions. I have also added
the calls for `w32-*-watch' functions, but this is untested.

I'll add the documentation and a NEWS entry once this feature has been
proven useful.

Any feedback is welcome.

Best regards, Michael.