message: Remove C++14 auto return type deduction that I accidentally introduced into
  `thrust::async::copy`.
diff: @@ -107,8 +107,7 @@ struct copy_fn final
  , ForwardIt&& first, Sentinel&& last
  , OutputIt&& output
  )
  -// THRUST_DECLTYPE_RETURNS(
  - { return
  + THRUST_DECLTYPE_RETURNS(
  copy_fn::call(
  thrust::detail::derived_cast(thrust::detail::strip_const(exec))
  // Synthesize a suitable new execution policy, because we don't want to
  @@ -119,8 +118,7 @@ struct copy_fn final
  , THRUST_FWD(first), THRUST_FWD(last)
  , THRUST_FWD(output)
  )
  - ; }
  -// )
  + )
  template <typename ForwardIt, typename Sentinel, typename OutputIt>
  __host__
  