Implemented multithreaded rendering in mapMandelLocationToIterationValues using mapMandelLocationSegmentToIterationValues function.  Best max num threads for my machine = 10 (probably because of varying length of rendering time for different areas of the Mandelbrot set since some values go up to maxIterations and some stop at 1 or 2 iterations, and this distributes the load and keeps each thread having an area of similar rendering time)