Pass self to lock methods.

This avoids frequent recomputation of
Thread::Current/pthread_getspecific.

Also add a futex based reader/writer mutex that is disabled.

Change-Id: I118fdb99ef1d1c4bfda6446ba3a0d8b6ab31eaee
diff --git a/src/logging.cc b/src/logging.cc
index a0c07cf..48785c5 100644
--- a/src/logging.cc
+++ b/src/logging.cc
@@ -16,6 +16,7 @@
 
 #include "logging.h"
 
+#include "mutex.h"
 #include "runtime.h"
 #include "thread.h"
 #include "utils.h"