Missing header on activation.cc
Missing header on activation.cc

hvy/chainer,niboshi/chainer,chainer/chainer,okuta/chainer,okuta/chainer,niboshi/chainer,niboshi/chainer,hvy/chainer,wkentaro/chainer,chainer/chainer,wkentaro/chainer,wkentaro/chainer,wkentaro/chainer,pfnet/chainer,hvy/chainer,okuta/chainer,hvy/chainer,chainer/chainer,niboshi/chainer,chainer/chainer,okuta/chainer