drop native stack traces from continuations; they're expensive to compute, not actually used, and could be computed on demand
drop native stack traces from continuations; they're expensive to compute, not actually used, and could be computed on demand

svn: r17667

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