Windows: Fix compiler warnings in accessibility.

Change-Id: Id9ffe1069116f25b89df85337a75dae54b5beec5
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@nokia.com>
Reviewed-by: Andriy Golovnya <andriy.golovnya@googlemail.com>

src/plugins/platforms/windows/qwindowsaccessibility.cpp

@@ -1126,6 +1126,8 @@ HRESULT STDMETHODCALLTYPE QWindowsAccessible::put_accValue(VARIANT, BSTR)
 // moz: [important]
 HRESULT STDMETHODCALLTYPE QWindowsAccessible::accSelect(long flagsSelect, VARIANT varID)
 {
+    Q_UNUSED(flagsSelect);
+    Q_UNUSED(varID);
     showDebug(__FUNCTION__, accessible);
     if (!accessible->isValid())
         return E_FAIL;