What if Easy Rider was a Spanish anthology film? Although crude, that's    one way of getting at 1969's Los Desafios, a trilogy of vignettes          directed by Claudio Guerin, Jose Luis Egea, and Victor Erice. Dean Selmier       appears in all three, playing a hippie, an American soldier, and a wanderer.   In each episode, he meets an untimely, unsightly end. With Francisco Rabal,    Alfredo Mayo, and Julia Pena. Winner of the Silver Seashell at the San         Sebastian Film Festival. In Spanish with NO subtitles.                           Claudio Guerin/Jose Luis Egea/Victor Erice---Spain---1969---100 mins.