[ocaml-platform] [Coq-Club] Coq opam package

[Thomas Refis]

Another possibility is to not update a package right away when a knew
optional dependency is available, but wait for the next "opam
upgrade". And adding a "--ignore <package>" option to the upgrade
command would be nice as well.

The fact that you don't have a choice when installing a package to
update all the package that may use it or not, is imho really
frustrating. I have indeed had to recompile coq a few times as well,
and the experience gets more annoying every time.

Thomas.