RFR: vcs: add support for Mercurial 5.3

[Robin Westberg]

On Fri, 14 Feb 2020 08:29:32 GMT, Erik Helin <ehelin at openjdk.org> wrote:

> Hi all,
> 
> please review this patch that adds support for Mercurial 5.3. Mercurial changed its internal API slightly for 5.3, see [here](https://phab.mercurial-scm.org/D7406) for the relevant commit. The fix is simple, just make a `tuple` for the returned value `repo.status`.
> 
> Testing:
> - `make test` with _both_ hg 4.9 and 5.3
> 
> Thanks,
> Erik

All builds passed, looks good!

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Marked as reviewed by rwestberg (Reviewer).

PR: https://git.openjdk.java.net/skara/pull/438