updated Darcs support for VC (vc-darcs.el)

[Dave Love]

I've seen statements that the assigned vc-darcs.el doesn't support the
current version of Darcs, although it did before Darcs 2 was released.
However, I hadn't re-posted it, so here's the current version.

It should work with Darcs 1 and 2 in Emacs 21 and 22.  It seems
basically to work in the incompatible development (?) version of VC,
though I don't understand properly what the back end functions are
supposed to do, and I've only tried it briefly on a single file with
Ubuntu's current `emacs-snapshot'.

vc-darcs.el
Description: application/emacs-lisp