Implement fixed-format floating point through FLONUM-TO-DIGITS.
Essentially this means a whole heap of hairy logic in
FLONUM-TO-STRING, and the deletion of the Steele & White
... fixes (format nil "~@F" 1.23)
... fixes (format nil "~3F" -0.0)
... fixes (format nil "~G" 1d23)
... fixes (format nil "~E" 1d23)
... fixes bug 317
... does not fix bug 19, which I think is not a bug
... fixes all sorts of other stuff
It probably also breaks something, because test coverage of
this area is definitely patchy.