Allow extra _oasis files

[gildor478]

This feature request has been migrated from artifact #521 on forge.ocamlcore.org. It was assigned to user102.

user102 posted on 2010-02-03 13:48:06:

It should be possible to have a main _oasis file and several _oasis.extra-* (see cabal for more precise name).

In this extra files, we could overload _oasis values, create new section and extend already created (Extend Library ..., fails if it doesn't exist).