Fix warnings with latest rustc nightly
Fix warnings with latest rustc nightly

Turn off the trivial_numeric_casts lint for now, it's overly aggressive
when casting between typealiases.

kballard/rust-lua,green-panther/rust-lua,tempbottle/rust-lua,green-panther/rust-lua,kballard/rust-lua,tempbottle/rust-lua,beatgammit/rust-lua,beatgammit/rust-lua