Brands in recursive types result in interface being misplaced

Calling `t.brandCombinator` on a recursive feild results in something like this:

```
const Schema: t.RecursiveType> = t.recursion('Schema', () => t.brand(_Schema, (x): x is t.Branded<_Schema, XPropertiesBrand> => true, 'XProperties')
interface XPropertiesBrand {
readonly XProperties: unique symbol
})
```

The interface is placed within the recurisve expression.

That happens because of this line: https://github.com/gcanti/io-ts-codegen/blob/0be18841a50ceb0a45ade7f4bf0d9b365e33018c/src/index.ts#L788

One idea for a fix: another function instead of `printRuntime` (ie `printDefinitions`) could be used to print this sort of thing.