#5620 Convert OSXScreen into Objective C++

src/lib/platform/OSXScreen.h

@@ -344,4 +344,6 @@ private:
 	Mutex*					m_carbonLoopMutex;
 	CondVar<bool>*			m_carbonLoopReady;
 #endif
+
+	class OSXScreenImpl*	m_impl;
 };

src/lib/platform/OSXScreen.mm

@@ -112,7 +112,8 @@ OSXScreen::OSXScreen(IEventQueue* events, bool isPrimary, bool autoShowHideCurso
 	m_lastSingleClickYCursor(0),
 	m_autoShowHideCursor(autoShowHideCursor),
 	m_events(events),
-	m_getDropTargetThread(NULL)
+	m_getDropTargetThread(NULL),
+	m_impl(NULL)
 {
 	try {
 		m_displayID   = CGMainDisplayID();