You might call Boorman’s fortitude admirable, but you could also call it delusional. And it lends “Boorman and the Devil” the quality of a true-life Christopher Guest movie. For this is the unintentionally funny story of what happens when utterly unhinged and high-minded hubris becomes your guiding light. Boorman, and others associated with “Exorcist II,” know that they made an infamous disaster, yet the reason the film was a disaster still eludes them.