[multi-tty] Emacs port status

[Jason Rumney]

Thanks to some help from Dan Nicolaescu, I think we have reached a point
with the Windows port where I would be comfortable merging into the
trunk. There is still much to do - none of the extra functionality is
working, and -nw support is broken, but I don't think that is a
showstopper for Windows users. Some more testing while it is still on
the branch will be most welcome.

Maintainers of other ports may find it useful to look at the changelogs,
as the changes for other platforms will probably be similar.