mux: remove dead GET_STREAM_ADD_WAIT code

This makes no sense in a muxer which does not support adding streams
while muxing.

modules/demux/avformat/mux.c

@@ -496,11 +496,6 @@ static int Control( sout_mux_t *p_mux, int i_query, va_list args )
         *pb_bool = false;
         return VLC_SUCCESS;
 
-    case MUX_GET_ADD_STREAM_WAIT:
-        pb_bool = va_arg( args, bool * );
-        *pb_bool = true;
-        return VLC_SUCCESS;
-
     case MUX_GET_MIME:
     {
         char **ppsz = va_arg( args, char ** );

modules/mux/avi.c

@@ -280,11 +280,6 @@ static int Control( sout_mux_t *p_mux, int i_query, va_list args )
            *pb_bool = false;
            return VLC_SUCCESS;
 
-       case MUX_GET_ADD_STREAM_WAIT:
-           pb_bool = va_arg( args, bool * );
-           *pb_bool = true;
-           return VLC_SUCCESS;
-
        case MUX_GET_MIME:
            ppsz = va_arg( args, char ** );
            *ppsz = strdup( "video/avi" );

modules/mux/wav.c

@@ -138,11 +138,6 @@ static int Control( sout_mux_t *p_mux, int i_query, va_list args )
             *pb_bool = false;
             return VLC_SUCCESS;
 
-        case MUX_GET_ADD_STREAM_WAIT:
-            pb_bool = va_arg( args, bool * );
-            *pb_bool = true;
-            return VLC_SUCCESS;
-
         case MUX_GET_MIME:
             ppsz = va_arg( args, char ** );
             *ppsz = strdup( "audio/wav" );