Code review request: 7127660 (macosx) *Socket Async close not working

[Michael McMahon]

Could I get the following change reviewed please?

http://cr.openjdk.java.net/~michaelm/7127660/webrev.1/

The asynchronous close mechanism was not being compiled for Mac OS.
Also, the pthread mutexes used by this code, need to be explicitly 
initialized
on Mac, which was not being done previously (on Linux).

Thanks,
Michael.