* Change: In cumulus/plugins.block.macro, the METAL2 blockage was
    allowing horizontal tracks to be used but the METAL3 blockage
    was conflicting with the end of the perpandiculars.
      The router was not able to manage that, so we slightly expand
    the METAL2 blockage to encompass the unreachable track.
      For the same reason, add a METAL4 blockage over METAL2.