Add run-time eval of fused addition of 5 vectors

 - Add run-time comparison of the following implementations of addition
   of 5 vectors:
  - Naive C++ loops _(i.e., unfused)_.
  - Naive C++ loop _(i.e., fused)_.
  - Consecutive Thrust transforms _(i.e., unfused)_.
  - Single Thrust transform using zip-iterator and custom functor
    implementing sum of five values in a tuple _(i.e., fused)_.