RFR: 8072147: Preloading libjsig.dylib causes deadlock when signal() is called

[david buck]

Hi!

Please review my fix below:

bug report: https://bugs.openjdk.java.net/browse/jdk-8072147

webrev: http://cr.openjdk.java.net/~dbuck/8072147/webrev.00/

The fix is intentionally limited only to the platform (OSX/BSD) and 
scenario (signal() implemented by means of a direct call to sigaction()) 
where we can reasonably expect to see (and therefor test) this issue.

Fix has been manually tested for effectiveness by myself. "hotspot" test 
suite run and passed on all platforms.

Cheers,
-Buck