Dropped DMAs, split DMAs

[flamewing]

One issue with the DMA queue (which it shares with the original queues) is that it silently drops off DMAs if the queue is full. This leads to graphical corruptions due to misaligned art and sprite/plane maps.

Maybe I should add an option to generate hard errors (say, through a trap instruction) instead of dropping a DMA or DMA piece. This could be used in debug mode by hackers to see if they need to increase the size of the queue.

Something similar applies to split DMAs: there should be a flag for generating a hard-error when the need for splitting one DMA arises. This would allow hackers to easily find these cases, and align the problematic art appropriately.