choose an appropriate default audio library

panda/src/audio/config_audio.cxx

@@ -36,7 +36,15 @@ ConfigVariableInt audio_cache_limit
  PRC_DESC("The number of sounds in the cache."));
 
 ConfigVariableString audio_library_name
-("audio-library-name", "miles_audio");
+("audio-library-name", 
+#if defined(HAVE_RAD_MSS)
+ "miles_audio"
+#elif defined(HAVE_FMODEX)
+ "fmod_audio"
+#else
+ ""
+#endif
+ );
 
 ConfigVariableDouble audio_volume 
 ("audio-volume", 1.0f);