RFR: 8023720: setjmp/longjmp changes the process signal mask on OS X

[Staffan Larsen]

The original conversation about this problem is here:  http://mail.openjdk.java.net/pipermail/serviceability-dev/2013-August/011318.html 

In short, setjmp/longjmp on OS X messes up the signal mask and we should use _setjmp/_longjmp instead.

This change fixes two occurences in the jdk. There are a couple more in the client and hotspot areas which I will file followup bugs about.

webrev: http://cr.openjdk.java.net/~sla/8023720/webrev.00/

Thanks,
/Staffan