output: static audio_output_plugin list as array

Instead of having to register each output plugin, store them
statically in an array.  This eliminates the need for the List library
here, and saves some small allocations during startup.

src/main.c

@@ -136,7 +136,6 @@ static void version(void)
 
 	LOG("\n");
 	LOG("Supported outputs:\n");
-	loadAudioDrivers();
 	printAllOutputPluginTypes(stdout);
 }