Support OCaml 4.10.0

I just installed OCaml and this package, but I apparently need to downgrade my version of OCaml to use this package. An alternative might be to provide the user a setting to ignore the OCaml version at their own risk, since I realize it can take a lot of work to become fully compatible with a changed compiler version.

The issue names no files, tests, or entry points. Start by locating where the package checks the OCaml compiler version, then determine whether full 4.10.0 compatibility or an opt-out setting is intended; done means the package works with OCaml 4.10.0 or clearly supports the documented alternative.

Written by the indexing model from the issue text.