Add support for OCaml 4.10

[kit-ty-kate]

Currently reason does not support OCaml 4.10 and the first beta is around the corner. This PR adds support for OCaml 4.10

[anmonteiro]

Thanks, @kit-ty-kate!

I predict this is gonna need some 4.10 specific expected test outputs as in https://github.com/facebook/reason/blob/master/formatTest/errorTests/expected_output/comments1.re.4.09.0

Should probaly be enough to copy them from the 4.09 ones.

[jordwalke]

Can we just alias the 4.10 expected test outputs to the 4.09 ones since we don't expect any changes?

[kit-ty-kate]

@jordwalke was that what you were asking?

The CI image used is a different one because the ocaml/opam2 images haven't been updated for a month and I feel like testing beta version requires at least a recent enough version of the compiler. cc @avsm. ocurrent/opam are supposed to be the successor of ocaml/opam2 anyway, so why not use them. At the very least to show that everything works, I can remove it before this PR is merged if it's an issue.

[jordwalke]

Thanks for thinking about ocurrent/opam:. I just don't know anything about it. If you revert that part, I can merge this, or alternatively, if you could point me to somewhere that suggests that is the right/supported new opam image? I appreciate this pull request!

[anmonteiro]

hey @kit-ty-kate I think it's fine to use the ocurrent docker image, but you missed adding the pipeline for 4.10.0 here

[kit-ty-kate]

For information: the final release of OCaml 4.10.0 is expected next week

[kit-ty-kate]

OCaml 4.10.0 has now been released.