Portaudio: consistency with other aouts (and kill a warning)

modules/audio_output/portaudio.c

@@ -426,7 +426,7 @@ static int PAOpenDevice( aout_instance_t *p_aout )
         if( p_sys->deviceInfo->maxOutputChannels >= 6 )
         {
             val.i_int = AOUT_VAR_5_1;
-            text.psz_string = "5.1";
+            text.psz_string = _("5.1");
             var_Change( p_aout, "audio-device", VLC_VAR_ADDCHOICE,
                         &val, &text );
             msg_Dbg( p_aout, "device supports 5.1 channels" );