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

UserDB.cpp

@@ -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
@@ -18,6 +19,8 @@
 #include "UserDB.h"
 #include "Log.h"
 
+#if defined(USE_DMR) || defined(USE_P25) || defined(USE_NXDN)
+
 #include <cstdio>
 #include <cstring>
 #include <cctype>
@@ -187,3 +190,6 @@ char* CUserDB::tokenize(char* str, char** next)
 
 	return str;
 }
+
+#endif
+