Here is a patch containing some combination of rtoy's and my
approaches to address some of the float printing problems recently
Patch hits print.lisp (for flonum-to-string), target-format.lisp
(format-exp-aux) and test/print.impure.lisp (adding test cases)
I'm not completely happy with all this float printing stuff, but this
cleans up some issues, adds test cases, and if I send it now people
can (hopefully) poke at it and see what they think. It is pretty
deeply on my back burner today....