move libthread to libstb-hal

libthread/reentrant_mutex.cpp

@@ -0,0 +1,11 @@
+#include <reentrant_mutex.h>
+
+ReentrantMutex::ReentrantMutex() :
+	Mutex(PTHREAD_MUTEX_RECURSIVE)
+{
+}
+
+ReentrantMutex::~ReentrantMutex()
+{
+	//safely destroyed in ~Mutex();
+}