Android native thread相关

几个主要的source code路径：

/system/core/include/utils/threads.h

/system/core/include/utils/Thread.h

/system/core/include/utils/AndroidThreads.h

/system/core/include/utils/ThreadDefs.h

/system/core/include/system/thread_defs.h

/system/core/libutils/Threads.cpp