Propagate allow_unchaining to to_device of the gradient
Propagate allow_unchaining to to_device of the gradient

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