/* :call-seq:
 *    Sys::Host.info
 *    Sys::Host.info{ |i| ... }
 *
 * Yields a HostInfo struct containing various bits of information about
 * the local machine for each entry in the hosts table.  In non-block form,
 * returns an array of HostInfo structs.
 *
 * The Struct::HostInfo struct contains 5 fields:
 *
 * * name      (String)
 * * aliases   (Array)
 * * addr_type (Integer) => Typically 2 (AF_INET) or 28 (AF_INET6)
 * * length    (Integer) => Typically 4 (IPv4) or 16 (IPv6)
 * * addr_list (Array)
 */
static VALUE host_info(VALUE klass){