minor in FPUCheck
* better throw than handleerror
* better handle SIGNAL_NANS mode flags
style
fix SIGNAL_NANS wth GML
* SigNan cannot cause sync errors!
* fpu/sse precision mode flags are saved are per-process
* _while_ exception mode flags are per-thread! (and don't influence sync'ness)
reduce PFS update rate by 10%