Add NullModem support

NullModem.cpp

@@ -0,0 +1,35 @@
+/*
+ *   Copyright (C) 2011-2018 by Jonathan Naylor G4KLX
+ *
+ *   This program is free software; you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *   GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program; if not, write to the Free Software
+ *   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+
+#include "NullModem.h"
+#include "Log.h"
+
+CNullModem::CNullModem(const std::string& port, bool duplex, bool rxInvert, bool txInvert, bool pttInvert, unsigned int txDelay, unsigned int dmrDelay, bool trace, bool debug) :
+CModem(port, duplex,rxInvert, txInvert,pttInvert,txDelay, dmrDelay, trace, debug),
+m_hwType(HWT_MMDVM)
+{
+}
+
+CNullModem::~CNullModem()
+{
+}
+
+bool CNullModem::open(){
+	::LogMessage("Opening the MMDVM Null Modem");
+	return true;
+}