1.0.8.36: Improve MIPS (and HPPA) floating pooint support.

1.0.8.36: Improve MIPS (and HPPA) floating pooint support.
  - For MIPS/HPPA, the NaN signalling bit's meaning is inverted.
  - Implement FLOATING-POINT-MODES and SET-FLOATING-POINT-MODES in C.
  - Delete the corresponding VOPs.
  - Document the MIPS special "unimplemented" floating point trap.
  - Add handling of the floating point control word in C signal handlers.
  - Mark NAN-COMPARISIONS as expected failure on MIPS. (It still doesn't
    work due to a kernel bug, siginfo_t's si_code field doesn't get
    updated properly.)