I was working on issue #661 and noticed that github.com/kr/pty was dead
when I ran into a problem with that module on macOS (GOARCH == darwin).
Replace that dependency with github.com/creack/pty which is ostensibly
being actively maintained.
I also chose to remove a couple of obsolete module signatures at the
same time.
I started by writing tests for sys.Ioctl but after I had 100% coverage
of that function it occurred to me the function could be eliminated.
Related #1062
This simplifies the website toolchain to no longer depend on an external
repository, and allows developing the genblog command in lockstep with the needs
of the website.
Second half to PR #801, this updates to latest module dependencies.
Note: this pins golang.org/x/sys to an older version, as more recent
versions introduce a yet-to-be-determined bug on Darwin.