[ocaml-platform] New release of OPAM

[Thomas Gazagnaire]

Hi all,

I've released 0.9.4 yesterday. Main changes:
* Disable auto-removal of unused dependencies. This can now be enabled on-demand using `-a`
* Fix compilation and basic usage on Cygwin
* Fix BSD support (use `type` instead of `which` to detect existing commands)
* Add a way to tag external dependencies in OPAM files
* Better error messages when trying to upgrade pinned packages
* Display `depends` and `depopts` fields in `opam info`
* `opam info pkg.version` shows the metadata for this given package version
* Add missing `doc` fields in `.install` files
* `opam list` now only shows installable packages

Remark: compilation from the source archive seems to be broken on Linux, you'll need a patch[1] to make it work.

Tthe last 2 feature requests I'm working on before 1.0.0 are:
* https://github.com/OCamlPro/opam/issues/306 and
* https://github.com/OCamlPro/opam/issues/185

I don't have any blocker bugs anymore so I'm quite confident to announce the first stable release next week. I stil welcome patches to improving the portability of OPAM.

Best,
Thomas

[1] https://github.com/OCamlPro/opam/commit/fb6b37abfa2bfb39f5450fdc0c4ec9cd6b777fdd.diff