- Rework the wrapper support to check libpkg version as well as pkg_install
version.
- Add libfetch to _prebuild_libs.
- There are no new features introduced.
Notes: the API is not stable, so basically, do not use libpkg in your
projects for now. Also there's no manpage for libpkg yet, because the API
will change drastically. I repeat, do not use libpkg for now.
