Avoid unnecessary dynamic allocation when calling script functions.

Use tracer instead of rooting in ValueCloner, to avoid memory
allocations.

This was SVN commit r7770.

source/scriptinterface/AutoRooters.cpp

@@ -42,4 +42,9 @@ void AutoGCRooter::Trace(JSTracer* trc)
 	{
 		JS_CALL_OBJECT_TRACER(trc, m_Objects[i], "AutoGCRooter object");
 	}
+
+	for (size_t i = 0; i < m_Vals.size(); ++i)
+	{
+		JS_CALL_VALUE_TRACER(trc, m_Vals[i], "AutoGCRooter val");
+	}
 }