Make all of the rest of the code base be conditionally compiled.

DMRDataHeader.h

@@ -1,5 +1,5 @@
 /*
- *   Copyright (C) 2015,2016,2017 by Jonathan Naylor G4KLX
+ *   Copyright (C) 2015,2016,2017,2023 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
@@ -19,6 +19,10 @@
 #ifndef DMRDataHeader_H
 #define DMRDataHeader_H
 
+#include "Defines.h"
+
+#if defined(USE_DMR)
+
 class CDMRDataHeader
 {
 public:
@@ -52,3 +56,5 @@ private:
 
 #endif
 
+#endif
+