fix macro expander performance problem
fix macro expander performance problem

The problem is related to marks that should cancel eagerly when
a form passes through many layers of macro expansion, such as in
the sieve stress test for `syntax-rules'.

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