Include location list end column for rust lint

[jonhoo]

Fixes #599.

I've updated the tests in test/handler/test_rust_handler.vader by extracting the encountered values from the failed tests. Where does src/playpen.rs come from?

[w0rp]

I'll have to look into how to add highlights which span multiple lines to support end_lnum.

[w0rp]

Highlighting now supports problems spanning many lines, so this should all just work now.

[w0rp]

Cheers! 🍻