Update to Go 1.9

[ChimeraCoder]

Go 1.9 was recently released, so we should pull in the changes from upstream.

[meAbab]

@ChimeraCoder if you give me some hints, maybe I can help.

[ChimeraCoder]

Sure thing! The easiest way to do start might just be:

1. Check out a new feature branch on koro
2. Add the upstream golang/go repository as a new remote (git@github.com:golang/go.git)
3. Rebase the feature branch onto the master branch from upstream
4. Fix merge conflicts (there will definitely be some)
5. Make sure that the project still compiles, and that the resultant binary is still capable of running the "hello world" program we have in the root directory.

Now, that won't be everything right there, but if you submit that as a pull request, that takes care of the bulk of it. FYI, most of the changes are in src/cmd/compile/internal/gc/lex.go.

Let me know if you need any help!