Ocamldoc: do not ignore "-open" arguments

[Octachron]

This pull requests open the module listed as arguments of -open in the initial environment of ocamldoc
to mirror the behavior of ocaml, ocamlc and ocamldep.

Without this modification, the "-open" command option has no effect within ocamldoc.

[gasche]

It seems fine to me, but I'm worried about not having a testsuite for ocamldoc to insert test for this kind of features. I don't think it is the responsibility of this PR to provide one, but we should think about it.

[gasche]

(Could you squash the three commits?)

[gasche]

Squashed and merged, thanks!

[Octachron]

For this particular case, it could also make sense to test that all tools interpret the "-open" option
in a coherent way, since discrepancies between them can make build processes quite painful.

[shindere]

@gasche well spotted. Will do my best to take this into account and at
least record the idea so that it does not get lost.

[gasche]

@shindere what about using Mantis tags? If that sounds good to you I (or you) can create an issue to track this particular one with a "testsuite" tag.

[shindere]

@gasche Why not! If you have the possibility to do it that would be great, but if you can't I can have a look. The remark about the fact that "open" should be treated in a consistent way by all tools seems also very meaningful to me and if that can be verified by testing, at least to some extent, I'd say it's worth recording in a safe place.

[gasche]

PR#7274: a testsuite for ocamldoc
http://caml.inria.fr/mantis/view.php?id=7274

[shindere]

It seems there are actually already a few tests, see testsuite/tests/tool-ocamldoc* But there is definitely room for many others.

[gasche]

Oh, indeed. @Octachron, could you create a test then that check for -open support?

[Octachron]

Certainly, I would have a look.