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/api/mutex.h

@@ -0,0 +1,14 @@
+#ifndef __MUTEX_CONTROL_H__
+#define __MUTEX_CONTROL_H__
+
+/* Request ids for mutex_control syscall */
+
+#if defined (__KERNEL__)
+#define MUTEX_CONTROL_LOCK		L4_MUTEX_LOCK
+#define MUTEX_CONTROL_UNLOCK		L4_MUTEX_UNLOCK
+#endif
+
+#define L4_MUTEX_LOCK		0
+#define L4_MUTEX_UNLOCK		1
+
+#endif /* __MUTEX_CONTROL_H__*/