The video code now writes out a bmp file per-frame. With this patch
applied, the Nintendo logo is rendered in each frame.
There is still plenty of work to be done. Pretty much everything is
hardcoded to make the bootrom work.
Instead of calling cpu_cycle() and video_cycle() once per emulated
cycle, call cpu_cycle() once per emulated instruction. This should not
have any obvious effects on the emulation (as currently written),
because all of the memory reads and writes are done in the first
"cycle" of the instruction.
This patch results in a substantial performance gain (>100%, if I
recall correctly).
