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/kip.h

@@ -62,11 +62,11 @@ struct kip {
 	u32 thread_switch;
 	u32 schedule;
 	u32 getid;
+	u32 mutex_control;
 
 	u32 arch_syscall0;
 	u32 arch_syscall1;
 	u32 arch_syscall2;
-	u32 arch_syscall3;
 
 	u32 utcb;