Fix FSA parsing numbers incorrectly in json

[ElectreAAS]

Resolves #367

[art-w]

To avoid another surprise in the future, could we add another unit test that runs make bench in local-test-repo and check that the parser succeeds on the output? :) (it could be a more complex test that checks that the identified substrings parse correctly with Yojson, and are accepted by Current_bench_json)

[ElectreAAS]

Do we have a way to call make from inside ocaml? Otherwise the only thing that I can do is copy the json from the Makefile to a unit test

[art-w]

Yes there is Unix.open_process_in to run arbitrary shell commands (and grab their output... and perhaps Unix.chdir would also be useful here). I kind of like the idea that the unit tests are kept in sync with the local-test-repo rather than a static file, such that we don't forget to update them :)

[art-w]

Thanks!