Node 0.11.x support

With these changes, node_mdns builds and runs under Node 0.11.14 and nan 1.3 although I cannot say with certainty as amount of testing it received with these changes is too little.
Never seen it. Might be some old hack from 0.11.11 or 0.11.12, if so it should not be needed any more since 0.11.13.