New IDA plugin - N-Coverage

Finally, I added another IDA plugin which was written some months ago while doing the DRM analysis. N-Coverage was used to spot relevant code in the DRM system, although it actually turned out to be of minor use in that special case (due to all the anti reverse engineering techniques).
However, it was referenced in the DEFCON paper, so here it is. Don't expect too much of it, though. Needless to say, it comes with full source code.