reverted to old proof of dominoes_tile_row, given new treatment of #2+...
reverted to old proof of dominoes_tile_row, given new treatment of #2+...

MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle,MerelyAPseudonym/isabelle