[Libguestfs] GObject bindings - post-review patches

These patches address review comments from the original post. I don't propose to push these patches as-is, I would merge them into the relevant existing commits before pushing them. Having them as separate patches is purely a convenience for review. Merge into main gobject bindings patch: [PATCH 1/3] gobject: Add license to gobject/Makefile.am [PATCH 3/3] gobject: OCaml syntax cleanups Merge into bindtests patch: [PATCH 2/3] gobject: Check gjs is available for gobject bind tests