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

AX25Twist.cpp

@@ -17,6 +17,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_AX25)
+
 #include "Globals.h"
 #include "AX25Twist.h"
 
@@ -309,3 +312,5 @@ void CAX25Twist::setTwist(int8_t n)
   m_filter.pCoeffs = coeffs[twist];
 }
 
+#endif
+