fixed helper for win32
fixed helper for win32

okuta/chainer,keisuke-umezawa/chainer,wkentaro/chainer,niboshi/chainer,pfnet/chainer,chainer/chainer,hvy/chainer,hvy/chainer,niboshi/chainer,niboshi/chainer,tkerola/chainer,wkentaro/chainer,niboshi/chainer,chainer/chainer,chainer/chainer,okuta/chainer,wkentaro/chainer,hvy/chainer,hvy/chainer,keisuke-umezawa/chainer,keisuke-umezawa/chainer,okuta/chainer,keisuke-umezawa/chainer,wkentaro/chainer,okuta/chainer,chainer/chainer