message: only send extversion message if both peers are using the protocol
diff: @@ -534,7 +534,8 @@ bool ProcessMessage(CNode *pfrom, std::string strCommand, CDataStream &vRecv, in
  // Potentially mark this peer as a preferred download peer.
  UpdatePreferredDownload(pfrom);
  - if (pfrom->nServices & NODE_XVERSION)
  + // only send extversion message if both peers are using the protocol
  + if ((nLocalServices & NODE_XVERSION) && (pfrom->nServices & NODE_XVERSION))
  {
  // BU expedited procecessing requires the exchange of the listening port id
  // The former BUVERSION message has now been integrated into the xmap field in CXVersionMessage.
  