Use signals for cpu profiling on Mac OS X

Use signals for cpu profiling on Mac OS X

A while ago in r2315 Mac OS X cpu profiler implementation was changed to pause sampled thread instead of sending SIGPROF signal. That was done because at that point profiler send the signal to the whole process and it was handled on a random thread. Now that signal-based implementation uses pthread_kill it may well be used on Mac OS X too.

BUG=v8:2814
R=bmeurer@chromium.org, svenpanne@chromium.org

Review URL: https://codereview.chromium.org/23115005

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@16320 ce2b1a6d-e550-0410-aec6-3dcde31c8c00