[CM] cmn braille output

[Bill Schottstaedt]

With much help from Ruven Gottlieb, I've added the output-type :Braille
to cmn, and made some initial translations (brl-display in cmn4.lisp) so that

(cmn (output-type :Braille) treble c4 q full-double-bar)

will write a file containing

>/l?<k

which I think an Everest printer can turn into Braille.  The rest of
the translation is a small matter of software... No, actually it's
just a matter of going through tables of correspondences and typing
them in -- I'll do it as I find time.