Added a missing JUCE_API

modules/juce_events/messages/juce_MessageManager.h

@@ -201,7 +201,7 @@ public:
     /** A lock you can use to lock the message manager. You can use this class with
         the RAII-based ScopedLock classes.
     */
-    class Lock
+    class JUCE_API  Lock
     {
     public:
         /**