add scatter-add to support multiple integer arrays
add scatter-add to support multiple integer arrays

Conflicts:
	cupy/core/core.pyx

anaruse/chainer,wkentaro/chainer,ktnyt/chainer,cupy/cupy,okuta/chainer,chainer/chainer,jnishi/chainer,ronekko/chainer,niboshi/chainer,hvy/chainer,cupy/cupy,niboshi/chainer,hvy/chainer,ysekky/chainer,keisuke-umezawa/chainer,okuta/chainer,kashif/chainer,cupy/cupy,okuta/chainer,wkentaro/chainer,hvy/chainer,keisuke-umezawa/chainer,ktnyt/chainer,keisuke-umezawa/chainer,okuta/chainer,rezoo/chainer,jnishi/chainer,jnishi/chainer,chainer/chainer,aonotas/chainer,wkentaro/chainer,hvy/chainer,delta2323/chainer,pfnet/chainer,niboshi/chainer,keisuke-umezawa/chainer,cupy/cupy,jnishi/chainer,ktnyt/chainer,chainer/chainer,kiyukuta/chainer,ktnyt/chainer,niboshi/chainer,wkentaro/chainer,tkerola/chainer,chainer/chainer