FUEL: Remove key bindings of the form C-c <alphabetic>

FUEL: Remove key bindings of the form C-c <alphabetic>

Bindings of the form C-c <alphabetic> (e.g. C-c z) are traditionally
reserved in Emacs for user-defined keymaps, and shouldn't be used by
packages.

This patch removes all bindings of that form, replacing them by C-c
C-<alphabetic> (or simply preserving a previously existing binding).
E.g., C-c z becomes C-c C-z. In most cases, the binding with two C's
was already present.

The only change not following the above rule is C-c h in the listener,
which has become C-c C-w (because the C-h suffix is also 'taken' by
Emacs conventions).