Fix broken syscalls

The syscall interfaces seem to have changed since whenever this package
was written.
Fix error message

The syscall causing the error here is FCNTL, not IOCTL.
Merge pull request #6 from adammck/fix_for_go12

Fix for Go v1
Support non-standard baud rates

This sets the baud rate using the IOSSIOSPEED ioctl, rather than as part
of the termios options, which allows arbitrary speeds.
Update docs for OpenOptions.BaudRate