It turns out to not be too much of a performance issue to allocate
a new frame each time one is produced, so to reduce lock contention
I added a queue where frames are added to and taken from without
locking the frame for the whole update. I'm hoping this will give
more flexibility to frontend implementations, which can simply
skip or repeat frames if needed.
Mortal Kombat 2 was working but somewhere while getting the harte
tests to work, I fixed interrupts to change the flags before they're
pushed to the stack, in order to match the expected behaviour from
the tests when an address error occurs (sr is changed and the stack
push causes the error). I correctly saved the state of sr in the
function for group0 interrupts, to push to the stack later, but the
normal interrupts was saving sr *after* the flags were changed...
Now it saves sr beforehand
I also included some changes to the gfx interface to allow taking
frames, to fix a compile error introduced by the last commit.
I wanted to make this a bit more modular, so it's easier in theory to
write external crates that can reuse bits, and selectively compile in
bits, such as adding new systems or new cpu implementations
