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_create.c b/src/thread/pthread_create.c
index 6cbf85b..34cd993 100644
--- a/src/thread/pthread_create.c
+++ b/src/thread/pthread_create.c
@@ -37,10 +37,10 @@
 
 	__pthread_tsd_run_dtors();
 
-	__lock(self->exitlock);
+	LOCK(self->exitlock);
 
 	/* Mark this thread dead before decrementing count */
-	__lock(self->killlock);
+	LOCK(self->killlock);
 	self->dead = 1;
 
 	/* Block all signals before decrementing the live thread count.
@@ -54,7 +54,7 @@
 	 * been blocked. This precludes observation of the thread id
 	 * as a live thread (with application code running in it) after
 	 * the thread was reported dead by ESRCH being returned. */
-	__unlock(self->killlock);
+	UNLOCK(self->killlock);
 
 	/* It's impossible to determine whether this is "the last thread"
 	 * until performing the atomic decrement, since multiple threads