fix bug that affects `free-identifier=?'
fix bug that affects `free-identifier=?'

This bug is in the "amazing that it lurked for years" category,
as well as the "stupid use of C preprocessor" category.

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket