wishlist: format ~:@C to print "user readably"

[mon_key]

(format t "Please type ~:@C to continue: " #\Soh)
(format t "Please type \"~:@C\" to continue: " #\Soh)
=> Please type "Soh" to continue:

Would be nice if this returned:
=> Please type "C-SPC" to continue:

Or, some non-Emacs equivalent :)

,----
|
| 22.3.1.1 Tilde C: Character
|
| ~:@C prints what ~:C would, and then if the character requires unusual shift
| keys on the keyboard to type it, this fact is mentioned. For example,
|
| (format nil "~:@C" #\Control-Partial) => "Control-<PARTIAL> (Top-F)"
|
| This is the format used for telling the user about a key he is expected to type,
| in prompts, for instance. The precise output may depend not only on the
| implementation, but on the particular I/O devices in use.
|
`----

SBCL 1.0.45.3