Last evenings scheduled 80th birthday party for Vic Skolnick, co-founder with his beloved Charlotte Sky of the anti-multiplex known in these parts as the Cinema Arts Centre, actually was a belated celebration. Officially, Skolnick waded into his four score years on April 25. June, however, seemed a more favorable date for throwing a party, what with potential partygoers all hyped over flowerings of landscape and sunnier skies.