Reduce and move remaining ph files to perl-ph
    
    Sys::Hostname::hostname() uses ghname() from XS and thus does not fall
    back to ph files.
    
    Net::Domain::_hostdomain() indeed tries ph files, but Linux does not
    provide getdomainname() syscall. Then it falls back to another
    solution.
    
    Net::Domain::_hostname() falls back to POSIX::uname() successfully.
    
    perlfunc/ioctl() recommends sys/ioctl.ph.
    perlfunc/syscall() recommends syscall.ph.
    perlfaq5 recommends sys/syscall.ph.