Allow god-literal-key to be toggled

[federkamm]

The changes allow god-literal-key to be toggled. This is necessary when modified keys follow literal keys in a key sequence. E.g. C-x r M-y for copy-rectangle-as-kill can now be entered as x SPC r SPC g y.

Should the version be bumped to 2.19.0?

Shortcomings: C-SPC can still not be entered within a key sequence. E.g. C-x r C-SPC for point-to-register can't currently be entered in god-mode.

Beside the Ecukes test, the code was verified with

(defun god-mode-translate (key-string)
  (let* ((key-list (cl-coerce key-string 'list))
         (pop-key-list (lambda (&rest _) (pop key-list)))
         god-literal-sequence string-so-far)
    (advice-add 'read-event :override pop-key-list)
    (unwind-protect (cl-loop for key = (read-event) unless key return string-so-far
                             do (let ((sanitized-key (god-mode-sanitized-key-string key)))
                                  (setq string-so-far (god-key-string-after-consuming-key sanitized-key string-so-far))))
      (advice-remove 'read-event pop-key-list))))

(let ((god-mode-tests '("x x x" "C-x x C-x"
                        "x xx" "C-x x x"
                        "xxx" "C-x C-x C-x"
                        "x xx xx x" "C-x x x C-x C-x x"
                        "x x gx" "C-x x M-x"
                        "x xgx" "C-x x g x"
                        "x  x" "C-x C-x"
                        "x   x" "C-x x")))
  (cl-loop for (input output) on god-mode-tests by #'cddr
           for translation = (god-mode-translate input)
           for success = (string= translation output)
           count (not success)
           unless success do (message "%S => %S =/= %S" input translation output)))

[darth10]

Thanks for this great improvement!

I've added a couple comments regarding indentation.

Generally, it would be good to keep new features behind a custom var, but I think in this case it would be more effort than it's worth.
We can always add a var later if needed.

Should the version be bumped to 2.19.0?

Let's not worry about that for now - version bumps are for stable versions anyways.
I'll bump it after some time, once others have had a chance to try out these changes.

[darth10]

Closes #135.