Evil Is Only Skin Deep In 'Star Trek 9: Insurrection.' By James DiGiovanna THE LEGENDARY SEXUAL prowess of the Star Trek fan (whom I prefer to call a "Trekkie," the term "Trekker" clearly having been invented by the same language commissars who brought us "differently beautiful," "gravitationally challenged" and "unbreakable comb") is no urban legend: Those who have experienced the extreme delights that pass when pointy ears are tickling their thighs know what I'm talking about. There's nothing that turns an ordinary dermatologist or C++ programmer into a Svengali of sensuality like immersion in the geekertronic future of über-nerd Gene Roddenberry's