Pass chain locked variables where needed

This commit does not change behavior. All it does is pass new function
parameters.

It is easiest to review this change with:

    git log -p -n1 -U0 --word-diff-regex=.

src/threadsafety.h

@@ -54,4 +54,15 @@
 #define ASSERT_EXCLUSIVE_LOCK(...)
 #endif // __GNUC__
 
+// Utility class for indicating to compiler thread analysis that a mutex is
+// locked (when it couldn't be determined otherwise).
+struct SCOPED_LOCKABLE LockAnnotation
+{
+    template <typename Mutex>
+    explicit LockAnnotation(Mutex& mutex) EXCLUSIVE_LOCK_FUNCTION(mutex)
+    {
+    }
+    ~LockAnnotation() UNLOCK_FUNCTION() {}
+};
+
 #endif // BITCOIN_THREADSAFETY_H