Windows: Fix exit crash related to deletion of platform screens.

Do not delete screens in the destructor as this might call
back to the Windows and use QWindowsContext.

Change-Id: I5e66e480d4b6ddb8b17cc92e4bef93013e336be6
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>

src/plugins/platforms/windows/qwindowscontext.cpp

@@ -291,6 +291,7 @@ QWindowsContext::~QWindowsContext()
     if (d->m_oleInitializeResult == S_OK || d->m_oleInitializeResult == S_FALSE)
         OleUninitialize();
 
+    d->m_screenManager.clearScreens(); // Order: Potentially calls back to the windows.
     m_instance = 0;
 }
 

src/plugins/platforms/windows/qwindowsscreen.cpp

@@ -304,11 +304,6 @@ QWindowsScreenManager::QWindowsScreenManager() :
 {
 }
 
-QWindowsScreenManager::~QWindowsScreenManager()
-{
-    qDeleteAll(m_screens);
-}
-
 /*!
     \brief Triggers synchronization of screens (WM_DISPLAYCHANGE).
 

src/plugins/platforms/windows/qwindowsscreen.h

@@ -114,7 +114,8 @@ public:
     typedef QList<QWindowsScreen *> WindowsScreenList;
 
     QWindowsScreenManager();
-    ~QWindowsScreenManager();
+
+    inline void clearScreens() { qDeleteAll(m_screens); m_screens.clear(); }
 
     void handleScreenChanges();
     bool handleDisplayChange(WPARAM wParam, LPARAM lParam);