Fuzz the parser with afl

[pczarn]

I didn't take a good look, but fuzzing pointed out one minor mistake. I'll try to fuzz more. I expect using a serialized grammar format will be best. Perhaps the input token string should be over afl's control as well.

[pczarn]

I made a parser fuzzer for contracting work. The solution is taken from this reddit comment https://www.reddit.com/r/ProgrammingLanguages/comments/l0doct/how_to_use_fuzzing_to_test_an_arbitrary/