5′-Aminohydroxymethylene-1′,2′-dichloro-spiro[7H-pyrano[3,2-c;5,6-c′]dichromene-7,4′-cyclohex-2′-ene]-3′,6,6′,8-tetraone dimethylformamide disolvate, a spiro compound from the reaction of 4-hydroxycoumarin with 2,3-dichloro-5,6-dicyanobenzoquinone