Windows: Handle WM_SYSCOLORCHANGE as theme change.

Task-number: QTBUG-34170

Change-Id: I6ca11ab67c1e2752300fc167fb8f3c4f0d9ae2b8
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>

src/plugins/platforms/windows/qtwindowsglobal.h

@@ -204,6 +204,9 @@ inline QtWindows::WindowsEventType windowsEventType(UINT message, WPARAM wParamI
     case WM_DISPLAYCHANGE:
         return QtWindows::DisplayChangedEvent;
     case WM_THEMECHANGED:
+#ifdef WM_SYSCOLORCHANGE // Windows 7: Handle color change as theme change (QTBUG-34170).
+    case WM_SYSCOLORCHANGE:
+#endif
         return QtWindows::ThemeChanged;
     case WM_DWMCOMPOSITIONCHANGED:
         return QtWindows::CompositionSettingsChanged;