::Type should not be defined

```ruby
# good

class XType
  def initialize x
  end
end

p XType.new :x

# bad

class Type
  def initialize x
  end
end

p Type.new :x
```

er even:

```
10000 % ruby -e 'abort if defined?(Type)'
10001 % maglev
10002 % ruby -e 'abort if defined?(Type)'
a RubySystemExit occurred (error 2752)
topaz 1> exit
```