Add key description in `dvorak-mode-substitute'.
Make dvorak-mode-translate detect cons events.

We use key-definition for [(control ?c) (control ?d)] and similar
bindings definitions.
Don't translate [(32 . 64)] diapason bindings.

It commonly used to define multiple `self-insert-command' bindings at
ones.  We doesn't need to translate it.  Close #2.