fix build

fixes:
- warning , line with more than 100 chars on align_columns.rs
- changed syntax on subslice match on 24_game_solve.rs (see pull 17054 on rust-lang/rust)
- uint overflow on luhn_test.rs


theoretically we could just suppress the warning in this case, but the >100 chars lint does not seem to be included in Rust. I think it comes from our own build script, and I don't know if it's possible to suppress those: 
https://github.com/Hoverbear/rust-rosetta/blob/master/build.sh#L126