alloc stacks by calloc, not malloc
alloc stacks by calloc, not malloc

omasanori/picrin,ktakashi/picrin,picrin-scheme/picrin,koba-e964/picrin,picrin-scheme/picrin,ktakashi/picrin,koba-e964/picrin,dcurrie/picrin,leavesbnw/picrin,koba-e964/picrin,dcurrie/picrin,ktakashi/picrin,leavesbnw/picrin,leavesbnw/picrin,omasanori/picrin