Created by: luotao1

Suggested in https://github.com/PaddlePaddle/Paddle/pull/19510 changes to paddle::framework::vectorize() function.

• This PR remove std::vector<int> vectorize2int(const DDim& ddim) in ddim.h
• When updating all framework::vectorize2int to framework::vectorize<int>, we find that warpctc_cudnn_op.cu.cc uses the old framework::vectorize2int interface. Discussed with @wanghaoshuang, since warpctc-cudnn implementation always has accuracy-diff in both python2.7 and python3.5, and it will not be maintained later, this PR remove it.