Make AX.25, DMR, P25, NXDN and FM selectable at compile time.

AX25TX.cpp

@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25TX.h"
 
@@ -184,3 +187,5 @@ bool CAX25TX::NRZI(bool b)
     return m_nrzi;
 }
 
+#endif
+