rect: Trivial comment correction.
rect: Unions.
rect: s/normalized/normalize.

This change is to make normalize/intersect/unionize into verbs,
since union can't be a function name.
rect: Updated intersect naming.

- intersect() now matches naming for normalize/intersect/unionize.
rect: Updated unionize naming.

- unionize() now matches naming for normalize/intersect/unionize.

We can't name a function "union", so the union of 2 rects can't be a noun.
That's probably for the better. Functions should (typically) be verbs, yes?
rect: empty().
rect: Trivial changes in negation test.

- Made fixture members const.
- Fixed wrapping in table.
rect: Added null case to normalize test.
rect: size().
rect: Implemented empty() in terms of size().