optimize insertionsort: one less loop variable, one more addition, unconditional first step
optimize insertionsort: one less loop variable, one more addition, unconditional first step

svn: r17227

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