rem: WMCreateTreeBagWithDestructor(void (*destructor)(void*))
add: WMCreateTreeBagWithDestructor(WMFreeDataProc *destructor)
context: WMCreateTreeBagWithDestructor(void (*destructor)(void*)){    WMBag *bag;    bag = wmalloc(sizeof(WMBag));    memset(bag, 0, sizeof(WMBag));    bag->nil = wmalloc(sizeof(W_Node));    memset(bag->nil, 0, sizeof(W_Node));    bag->nil->left = bag->nil->right = bag->nil->parent = bag->nil;    bag->nil->index = WBNotFound;    bag->root = bag->nil;    bag->destructor = destructor;    return bag;}