dwmapi: Add DwmEnableComposition stub.

dlls/dwmapi/dwmapi.spec

 100 stub @
 101 stub @
-102 stub DwmEnableComposition
+102 stdcall DwmEnableComposition (long)
 103 stub @
 104 stub @
 105 stub @

dlls/dwmapi/dwmapi_main.c

@@ -59,3 +59,13 @@ HRESULT WINAPI DwmIsCompositionEnabled(BOOL *enabled)
     *enabled = FALSE;
     return S_OK;
 }
+
+/**********************************************************************
+ *           DwmEnableComposition         (DWMAPI.102)
+ */
+HRESULT WINAPI DwmEnableComposition(UINT uCompositionAction)
+{
+    FIXME("(%d) stub\n", uCompositionAction);
+
+    return S_OK;
+}