Add CPU implementation of SRU_Compute(), eg. for inference on machines without NVidia GPUs. Only tested with bidirectional layers. Only tested with `k = 4`.
Add CPU implementation of SRU_Compute(), eg. for inference on machines without NVidia GPUs. Only tested with bidirectional layers. Only tested with `k = 4`.

taolei87/sru,taolei87/sru,taolei87/sru