Added mutex_control syscall for userspace mutexes.

- Compiles and Codezero runs as normal without touching mutex implementation
- Mutex implementation needs testing.

The mutex control syscall allows userspace programs to declare any virtual
address as a mutex lock and ask for help from the kernel syscall
for resolving locking contentions.

include/l4/lib/wait.h

@@ -10,6 +10,8 @@ struct waitqueue {
 	struct ktcb *task;
 };
 
+#define WAKEUP_ASYNC			0
+
 enum wakeup_flags {
 	WAKEUP_INTERRUPT = (1 << 0),
 	WAKEUP_SYNC	 = (1 << 1)
@@ -74,5 +76,7 @@ void wake_up(struct waitqueue_head *wqh, unsigned int flags);
 int wake_up_task(struct ktcb *task, unsigned int flags);
 void wake_up_all(struct waitqueue_head *wqh, unsigned int flags);
 
+int wait_on(struct waitqueue_head *wqh);
+
 #endif /* __LIB_WAIT_H__ */