Kernel/LibC: Implement pthread_self

userspace/libraries/LibC/include/sys/syscall.h

@@ -92,6 +92,7 @@ __BEGIN_DECLS
 	O(SYS_HARDLINKAT,		hardlinkat)		\
 	O(SYS_PTHREAD_CREATE,	pthread_create)	\
 	O(SYS_PTHREAD_EXIT,		pthread_exit)	\
+	O(SYS_PTHREAD_SELF,		pthread_self)	\
 
 enum Syscall
 {

userspace/libraries/LibC/pthread.cpp

@@ -47,3 +47,8 @@ void pthread_exit(void* value_ptr)
 	syscall(SYS_PTHREAD_EXIT, value_ptr);
 	ASSERT_NOT_REACHED();
 }
+
+pthread_t pthread_self(void)
+{
+	return syscall(SYS_PTHREAD_SELF);
+}