NPD just published its latest plotting of the great American smartphone OS rivalry, and although the report covers annual rather than quarterly trends, it's perhaps more interesting to hold it up against the previous set of figures we saw — those for Q2 2011. Back then, Google's OS had a 52 percent share, but these new figures suggest a marginally better performance of 53 percent between January and October. Meanwhile, iOS's 29 percent share is identical to what we saw in Q2, hinting that it…