The debut novel that launched an astonishing literary career, Tempest-Tost is a magnificent display of Robertson Davies's legendary wit and the first novel in the Salterton Trilogy.     An amateur production of The Tempest provides a colourful backdrop for a hilarious look at unrequited love. Mathematics teacher Hector Mackilwraith, stirred and troubled by Shakespeare's plays, falls in love with the beautiful Griselda Webster. When Griselda shows that she h