tweak JIT generation of fixnum mult with a constant argument
tweak JIT generation of fixnum mult with a constant argument

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