* floating point -> integer conversions.
    x86 defines that overflow/underflow
    results in 1<<15, 1<<31, 1<<63 for
    int16, int32, int64.  when building the
    unsigned conversions out of the native signed
    ones, 8g turns overflow/underflow into zero.
    the spec does not say what should happen.

  * many tiny bug fixes.  can run a large number
    of files from go/test now, and can fmt.Printf.

  * struggling with byte register allocation
    and float32 computation.

R=ken
OCL=29642
CL=29811