Make D-Star, System Fusion, M17, and POCSAG optional.

DStarTX.cpp

@@ -18,6 +18,9 @@
  */
 
 #include "Config.h"
+
+#if defined(MODE_DSTAR)
+
 #include "Globals.h"
 #include "DStarTX.h"
 
@@ -446,3 +449,5 @@ uint8_t CDStarTX::getSpace() const
   return m_buffer.getSpace() / (DSTAR_DATA_LENGTH_BYTES + 1U);
 }
 
+#endif
+