1) Decouple SysBus from Gpu
2) Split Gpu rendering function into separate modules
3) Cleanup
Former-commit-id: 0435ad1c9c1de72ed50769fabfea7c5f33b670e0
I have fought very hard against the rust ownership model,
In the end for DMA to play nice with my code, I had to resort to use
unsafe code for now..
The DMA implementation itself is not accurate to say the least, but will
have to do for now.
Tonc's dma_demo.gba plays but with a visual glitch.
Former-commit-id: 3b9cdcb2d09c78701290f2c48b77f9f3487e85c9
