Support for Mac OSX
Support for Mac OSX

- We need to use pthread_setname_np on OSX to set thread names.
- clock_gettime is called clock_get_time on OSX and works a bit differently.

Change-Id: Ic5dcca9eca363e16447d7d0f852494f35f28dee6
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/5305
Reviewed-by: Adar Dembo <866ca730bfc7f544e3ebce604ceeba4879f23df0@cloudera.com>
Reviewed-by: Henry Robinson <3eca10f30041813f045165784e24b5a950a6cc7e@cloudera.com>
Tested-by: Jean-Daniel Cryans <4bf4c125525b8623ac45dfd7774cbf531df19085@cloudera.com>

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