Revert "Remove workaround for 9.2 compiler bug."

Revert "Remove workaround for 9.2 compiler bug."

This reverts commit 7828111b77fb53e34b365abc775148f49eabe1d2.

I haven't tracked this down because the stack trace is full of frames
in the compiler for which we don't install debug data but the symptom
is:

;  Compiling file: "./floenv.bin" => "./floenv.com"...
;The object +inf.0, passed as the first argument to flonum-normalize, is not the correct type.

First few frames suggest this is in flo:->rational called by something
in RTL CSE.