After the deep darkness that has pervaded area theaters during the past few weeks -- most notably with heavyweight dramas by Brecht, Büchner and Kafka -- the first lilting notes of an impending musical summer can be heard. This weekend (through May 9) the Kirkwood Theatre Guild concludes its production of Damn Yankees.Kirkwood Theatre GuildWhen it made its debut in 1955, Damn Yankees was only the second show from neophyte producer Hal Prince, who would emerge as the most prolific producer-direc