Fix memory leak in coalesce. (pytorch#1460)

Fixes pytorch#1449. For future reference, we should have a doc explaining our ref-counting conventions; it looks like this bug slipped by because we assumed that newTensor was taking ownership of the pointers it was passed in. Signed-off-by: Edward Z. Yang <ezyang@fb.com>

Author: ezyang

torch/lib/THCS/generic/THCSTensor.cu

@@ -164,6 +164,8 @@ THCSTensor *THCSTensor_(newCoalesce)(THCState *state, THCSTensor *self) {
 
  THCIndexTensor_(free)(state, indices);
  THCTensor_(free)(state, values);
+ THCIndexTensor_(free)(state, newIndices);
+ THCTensor_(free)(state, newValues);
 
  dst->coalesced = 1;
  THCudaCheck(cudaGetLastError());