Add language definition for Haskell

This pull request adds language definitions for Haskell. While this has been tested to work with a few example programs, I havn't tested it in practice.
I'd love to maintain these language definitions in the future!
Merged too fast, there was a comma missing. :wink: 
Just added in 011e430c6249e8c5abe356789560b2aef1998353