dwmapi: Add DwmEnableMMCSS stub.
diff --git a/include/dwmapi.h b/include/dwmapi.h
index 710e3f4..551138e 100644
--- a/include/dwmapi.h
+++ b/include/dwmapi.h
@@ -32,6 +32,7 @@
 DECLARE_HANDLE(HTHUMBNAIL);
 
 DWMAPI DwmEnableComposition(UINT);
+DWMAPI DwmEnableMMCSS(BOOL);
 DWMAPI DwmExtendFrameIntoClientArea(HWND,const MARGINS*);
 DWMAPI DwmGetColorizationColor(DWORD*,BOOL);
 DWMAPI DwmIsCompositionEnabled(BOOL*);