Film noir fan alert!   As announced by Eddie Muller of the Film Noir Foundation on these boards during the summer, TCM is showing director Andre de Toth's Pitfall this week.   And this one is a goodie. Dick Powell plays an insurance investigator who has a perfect family in a perfect home in the suburbs. And he's bored. That will only lead to trouble for him, especially when he meets a film noir icon, Lizabeth Scott.   The real trouble for his character, however, will come in the hulking fo