理解Mach Port

参考文档：

1. http://robert.sesek.com/thoughts/2012/1/debugging_mach_ports.html

2. Mach 3 Kernel Interfaces

3. http://www.foldr.org/~michaelw/log/computers/macosx/task-info-fun-with-mach

3. Mach 3 Kernel Principles

4. http://docs.huihoo.com/darwin/kernel-programming-guide/boundaries/chapter_14_section_4.html

5. http://www.mikeash.com/pyblog/friday-qa-2013-01-11-mach-exception-handlers.html