git rid of needless memcpy
git rid of needless memcpy


Former-commit-id: e0f39178a1df1319ad97aafd9430ac8d81fb1e78
danielhers/dynet,clab/dynet,shuheik/dynet,xunzhang/dynet,danielhers/dynet,danielhers/dynet,chunyang-wen/dynet,xunzhang/dynet,chunyang-wen/dynet,shuheik/dynet,danielhers/dynet,xunzhang/dynet,shuheik/dynet,clab/dynet,shuheik/dynet,clab/dynet,clab/dynet,clab/cnn,chunyang-wen/dynet,danielhers/dynet,clab/cnn,clab/dynet,danielhers/dynet,clab/dynet,shuheik/dynet,clab/cnn,danielhers/dynet,clab/dynet,xunzhang/dynet,shuheik/dynet,chunyang-wen/dynet,shuheik/dynet