RFR (S): 8245833: crash_with_sigfpe uses pthread_kill(SIGFPE) on macOS

[gerard ziemski]

hi all,

Please review this small and simple fix, that implements 
crash_with_sigfpe() in a way that causes an actual crash on macOS, so it 
doesn't need to fallback that uses pthread_kill()

bug link at https://bugs.openjdk.java.net/browse/JDK-8245833
webrev at http://cr.openjdk.java.net/~gziemski/8245833_rev1
passes Mach5 hs_tier1,2,3,4,5


cheers