use xp.linalg.norm and some fixes
use xp.linalg.norm and some fixes

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