Nominal classes and methods

[josh11b]

Add support for nominal (or "named") classes with encapsulation. Inheritance will be in a later proposal. Here is an example of the proposed syntax:

class Circle {
  fn Create(c: Point, r: f32) -> Self {
    return {.center = c, .radius = r};
  }
  fn Diameter[me: Self]() -> f32 {
    return me.radius * 2;
  }
  fn Expand[addr me: Self*](distance: f32);

  private var center: Point;
  private var radius: f32;
}

fn Circle.Expand[addr me: Self*](distance: f32) {
  me->radius += distance;
}

[chandlerc]

(Not actually done, just don't want to fail to mash "send". Made it up to "Access control".)

[chandlerc]

(ok, now finished!)

[chandlerc]

LGTM, probably just a TODO to add below.

[chandlerc]

Just posting a few suggestions that came up in a discussion with @josh11b and @mconst

[chandlerc]

(LGTM and all the thumbs up arrived.)