[Libguestfs] GObject bindings - post-review patches

[Matthew Booth]

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