Lwt_sysSourceSystem informations.
Not_available(feature) is an exception that may be raised when a feature is not available on the current system.
type feature = [ | `wait4| `get_cpu| `get_affinity| `set_affinity| `recv_msg| `send_msg| `fd_passing| `get_credentials| `mincore| `madvise| `fdatasync| `libev ]Features that can be tested.
The byte order used by the computer running the program.