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

UserDBentry.h

@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) 2020 by SASANO Takayoshi JG1UAA
+ *   Copyright (C) 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 +20,10 @@
 #if !defined(USERDBENTRY_H)
 #define USERDBENTRY_H
 
+#include "Defines.h"
+
+#if defined(USE_DMR) || defined(USE_P25) || defined(USE_NXDN)
+
 #include <string>
 #include <unordered_map>
 #include <vector>
@@ -48,3 +53,6 @@ private:
 };
 
 #endif
+
+#endif
+