Current position marker should be per-channel

[pulkomandy]

Since each channel has its own position, speed and rloop/lloop markers, the position marker should be drawn separately for each channel and for the breakpoints.

[pulkomandy]

[duggan] If you only wanted to draw each part once instead of each time it's used I might agree, but that wouldn't be useful either. With the current layout I think one position marker is sufficient because the individual parts will never be out of sync.