[Mammoth] Move Mutex and Semaphore to a separate folder.

lib/mammoth/src/semaphore.cpp

@@ -1,11 +0,0 @@
-#include "mammoth/semaphore.h"
-
-#include <zcall.h>
-
-#include "mammoth/debug.h"
-
-Semaphore::Semaphore() { check(ZSemaphoreCreate(&semaphore_cap_)); }
-Semaphore::~Semaphore() { check(ZCapRelease(semaphore_cap_)); }
-
-void Semaphore::Wait() { check(ZSemaphoreWait(semaphore_cap_)); }
-void Semaphore::Signal() { check(ZSemaphoreSignal(semaphore_cap_)); }