Adding entries to d{l,s}a-needed.txt

[Guido Günther <agx@sigxcpu.org>]

Hi,
I was a bit embarassed by the fact the I didn't get the sorting correct
(again) in dla-needed.txt:

So I came up with this:

   https://github.com/agx/emacs-tools/commit/2028d7a5548fb9cae641e45dc6f3a659f3b1839a

With that "C-, L" adds a new entry at the right position in
dla-needed.txt (for dsa-needed.txt there's xcpu-deb-add-dsa-needed as
well).

I'm not much of emacs lisp hacker so any improvements are welcome.
Cheers,
 -- Guido