Clean the fpu trap code:

Clean the fpu trap code:
- since there are no hardware fpu operation queues on real sparc64 hardware,
  don't bother declaring the relevant struct and fields.
- when an fpu instruction needs to be emulated, pass it directly to
  fpu_cleanup rather than fake its appearance in the fpu queue. While there,
  also pass the ready-to-use union sigval computed in trap() in case a
  signal needs to be delivered.

ok claudio@ kettenis@