Support x87 FPU

[perlun]

At the moment, running any FPU instruction leads to this:

The reason it's not supported is because the FPU registers are not handled by hardware multitasking (which we currently use). To support FPU, we would have to manually save them (for tasks that are using the FPU) and restore before context switching back to it, so it's a bit of work to fix this properly.