major code reorganization: it is now simpler than its srfi-45 roots, faster, and extensible (internally, to add new promise types)
major code reorganization: it is now simpler than its srfi-45 roots, faster, and extensible (internally, to add new promise types)

svn: r16754

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