Build fails on OpenBSD

[djmdjm]

Trying to build on OpenBSD fails in github.com/goburrow/serial. They fixed this in bfb69110f8dd4 but haven't tagged a release since.

Modifying go.mod to depend on this revision instead of v0.1.0 and running go mod download github.com/goburrow/serial to update go.sum lets the build succeed.

Would you be willing to accept a PR to switch to this version? goburrow/serial has had no commits in the last four years, so it's pretty stable.

Full error message below:

# github.com/goburrow/serial
../go/pkg/mod/github.com/goburrow/[email protected]/serial_bsd.go:30:18: undefined: syscall.B460800
../go/pkg/mod/github.com/goburrow/[email protected]/serial_bsd.go:78:45: fds.X__fds_bits undefined (type *syscall.FdSet has no field or method X__fds_bits)
../go/pkg/mod/github.com/goburrow/[email protected]/serial_bsd.go:79:46: fds.X__fds_bits undefined (type *syscall.FdSet has no field or method X__fds_bits)
../go/pkg/mod/github.com/goburrow/[email protected]/serial_bsd.go:86:6: fds.X__fds_bits undefined (type *syscall.FdSet has no field or method X__fds_bits)
../go/pkg/mod/github.com/goburrow/[email protected]/serial_bsd.go:92:13: fds.X__fds_bits undefined (type *syscall.FdSet has no field or method X__fds_bits)
../go/pkg/mod/github.com/goburrow/[email protected]/termios_bsd.go:10:19: cannot use speed (variable of type uint32) as int32 value in assignment
../go/pkg/mod/github.com/goburrow/[email protected]/termios_bsd.go:14: