Add unions and enums.

[Dich0tomy]

Status

Unions and enums parse properly, they don't do much for now.

Checklist

• Parsing enums and unions
• Basic enums and unions implementations in the VM
• ???

Syntax preview:

Enums:

enum MyEnum {
  name: Type;
  size: Int32;
}

Unions:

union MyUnion {
  name: Type;
  field: Type;
}

The following example parses and executes by vm properly:

class MyClass {
	a: Int32;
}
enum MyEnum { a: Int32; }

union MyUnion {
	a: Int32;
	b: Int32;
	c: MyEnum;
}

func main() {}