Variable name of doubled_task_number in code example for future

[Anjiang-Wei]

This is really a negligible issue. I would suggest changing the variable name of doubled_task_number to increment_task_number.
The related code is from

• futures.cc, Line22
  Future doubled_task_number = runtime->execute_task(ctx,producer_launcher);
• futures.cc, Line30-38

int subtask_producer(const Task *task,
		      const std::vector<PhysicalRegion> &regions,
		      Context ctx, 
		      Runtime *runtime)
{
  int subtask_number = *((int *) task->args);
  printf("\tProducer subtask %d\n", subtask_number);
  return subtask_number + 1;
}

[lightsighter]

Will see what @alexaiken thinks when he gets back, but it's fine with me if you would like to make a pull request.