Only output TypeScript type parameter constraint in parameter declaration

[Tarmil]

For example, in WebSharper.Control, we are currently outputting the following:

export function New<T0 extends Function>(Handlers:(T0)[]):DelegateEvent<T0 extends Function> {
  // ...
}

The extends Function constraint should only be present in the parameter declaration New<T0 ...> and not in the return type DelegateEvent<T0 ...>.