[CM] CMN

[Bill Schottstaedt]

I added x-close to the various ways of quitting cmucl, so
the byte=0 bug in xcmnw should be fixed.

And I merged Anders' draw-flags improvements into my version under
the variable names *straight-flag-dx* and *straight-flag-dy*.

On cmn horizontal spacing, there's pmn.lisp (for proportional
notation) and the spacing-hook, but it's true that this is too
hard to handle, especially on a measure-at-a-time basis.
The vertical spacing is set by things like staff-separation etc.

cmn was intended originally as a way to get a quick look at cm
(algorithmic) output in music notation (as opposed to a giant list of
instrument calls).  Way back in the days of Pla, I wrote a music
notation output program (was it EdPla? I can't remember my own
programs anymore), and it made my little tunes look so complex
and unperformable that I was smiling from ear to ear.