Add untried tests from scala/test/files/{pos,neg}

This PR adds all files from scala/test/files/pos and scala/test/files/neg, but procedure syntax was replaced by explicit Unit return types using the [rewrite tool](https://github.com/samuelgruetter/srewrite).

I also pushed the files to https://github.com/samuelgruetter/scala/tree/tests-without-procedure-syntax/test/files