Jit64: implement FPSCR related instructions

[Tilka]

No description provided.

[lioncash]

Does mffs set all the top bits of the destination register to 1? (hardware does this)

[Tilka]

@lioncash: Something like this? Did you do a hardware test? (I'd actually expect something like fctiw where it just makes it a NaN.)

riPS0(_inst.FD) = (0xFFFFFFFFull << 32) | FPSCR.Hex;

[lioncash]

I've re-run my tests, and you're correct; MFFS-ing a cleared FPSCR into a reg set to zero does produce a NaN. I might have been thinking about a different instruction.

[Tilka]

Haven't run into any problems.