WIP: ide: Force the use of a recent lablgtk
Without opam, this version is not the one provided in Debian stable. To be discussed.
In earlier version, the parameter ~parent of GToolbox.question_box does not exist. More recent version depends from OCaml version 4.06.0 or higher. Hence the choice for lablgtk 2.18.7.
Edited by DAILLER Sylvain