Support class static blocks

[tchetwin]

The class static blocks proposal introduces a new lexical scope nested within a class body:

class C {
    static {
        throw new Error("foo");
    }
}

[email protected] has implemented this (currently) Stage 3 proposal. playground

We should investigate what changes, if any, need to be made to pasta to support this feature.

---

This currently shows in Chrome console:

VM56:3 Uncaught Error: foo
    at <static_initializer> (<anonymous>:3:15)
    at <anonymous>:1:1