Add support for German and Swedish characters

In order to make it work with a US keyboard layout, these charcters are
implemented as hexadecimal Unicode character sequences in the Unix style:
<ctrl-shift-u> XXXX <enter>. This will not work on Windows and Emacs
requires a little bit of Elisp:

(defun keyboard-read-unicode ()
  "Insert a Unicode character by hexidecimal code."
  (interactive)
  (let* ((a (read-char "A" nil 2))
	 (b (read-char "B" nil 2))
	 (c (read-char "C" nil 2))
	 (d (read-char "D" nil 2))
	 (e (read-char "E" nil 2))
	 (all (string a b c d e))
	 (ch (string-to-number all 16)))
    (insert ch)))
(global-set-key [(control shift u)] 'keyboard-read-unicode)