[CM] Removing 'no-output' warning / values returns

[Bill Schottstaedt]

> > I've also thought that it would be nice if definstrument could, optionally, _
> > return values
> That's what run* was intended for -- doesn't it work in MCL?

Oops -- I think I see what the problem is -- I assumed tagbody
was like everything else and returned its last value, but it
always returns nil.  This change to defins.lisp line 500 or
so will export the instrument value:

		   (if (zerop clm::*interrupted*)
		       (let ((val nil))
			 (tagbody
			  (restart-case
			   (setf val (progn ,ins-code))
			   (nil ()
				:report "abort current note."
				(go C-INSTRUMENT-DONE)))
			  C-INSTRUMENT-DONE)
			 val))))