"warning: Captured variable 'x' not used in closure" presages a crash

[jruderman]

fn main() {
    let x = ~1;
    let lam_move = lambda[move x]() { };
    lam_move();
}

While compiling:

3:32 warning: Captured variable 'x' not used in closure

While running:

malloc: *** error for object 0x1: pointer being freed was not allocated

[graydon]

My guess is we're not treating the move-capture as cancelling the scope-exit cleanup on x. Should be a reasonably simple fix.