* Fixed stuff in the wall filter. Extended syntax:
     --filter wall         % open a wall (3x3 is the default value)
     --filter wall:2       % open a 2x2 wall
     --filter wall:3x2     % open a 3x2 wall
     --filter wall:2x1:0   % open a 2x1 wall, only display block 0
     --filter wall:2:0,3   % open a 2x2 wall, only display blocks 0 and 3
    For instance, if you have 2 computers listening to a network stream, on
    the left computer you use --filter wall:2x1:0 and on the right computer
    you use --filter wall:2x1:1