OpamSysPkgSourceSystem package
type status = {s_available : Set.t;Package available but not installed
*)s_not_found : Set.t;Package unavailable on this system
*)}System packages status
type to_install = {ti_new : Set.t;Package to install required by new opam packages
*)ti_required : Set.t;Package to install required by already install opam packages
*)}System packages to install. We need to split per purpose as some distribution need to keep up-to-date already installed system packages. See OpamSysInteract.install_packages_commands_t.