Bundle goocanvas 2.0 or 3.0
The distributions (we use for build: MSYS2 and brew.sh) starts to release the major version 3.0 of GooCanvas without keeping the version 2.0. Even if the numbering suggest it is a major release, it is not. GooCanvas project decide to follow the same numbering as Gtk and Gdk and so they changed their major version without any major change. GooCalendar supports both versions: https://goocalendar.tryton.org/bug36. Our build system should pick one of the available version.