unary move is not integrated into borrowck

[nikomatsakis]

This should fail:

fn foo(+x: ~int) -> int {
    let y = &*x;
    free(move x);
    *y
}

fn free(+x: ~int) {
}

fn main() {
}

but it does not. Should be a simple fix, add the appropriate line to check_loans.rs

[nikomatsakis]

Fixed now.