Rewrote the video seek code again. This time it is a _lot_ simpler and a lot better. For those interested: instead of letting ffmpeg choose the right final position, we let it preseek (maybe to I-frame in the rare case, that is implemented) and then scan for the correct frame on DTS basis by hand. We therefor only have to seek once and remove all those frame-jumping jerkiness, people noticed in the same step. Tested with msmpeg, hd-mpeg2 and DV.