seq reader: convert seq pos to segment pos for max rollout and precharge
seq reader: convert seq pos to segment pos for max rollout and precharge

The sequence position was wrongly used as a position in the first
(precharge) and last (rollout) segments.

xunchangguo/BMX,stuarthicks/bmx,Limecraft/ebu-bmx,Limecraft/ebu-bmx,xunchangguo/BMX,ebu/ebu-bmx,kierank/bmxlib-bmx,stuarthicks/bmx,ebu/ebu-bmx,Limecraft/ebu-bmx,ebu/ebu-bmx,xunchangguo/BMX,stuarthicks/bmx,kierank/bmxlib-bmx,kierank/bmxlib-bmx