consistently use the LOCK an UNLOCK macros

In some places there has been a direct usage of the functions. Use the
macros consistently everywhere, such that it might be easier later on to
capture the fast path directly inside the macro and only have the call
overhead on the slow path.
diff --git a/src/thread/pthread_setschedparam.c b/src/thread/pthread_setschedparam.c
index c4738d6..9e2fa45 100644
--- a/src/thread/pthread_setschedparam.c
+++ b/src/thread/pthread_setschedparam.c
@@ -3,8 +3,8 @@
 int pthread_setschedparam(pthread_t t, int policy, const struct sched_param *param)
 {
 	int r;
-	__lock(t->killlock);
+	LOCK(t->killlock);
 	r = t->dead ? ESRCH : -__syscall(SYS_sched_setscheduler, t->tid, policy, param);
-	__unlock(t->killlock);
+	UNLOCK(t->killlock);
 	return r;
 }