NameResolver::resolveSignature does not resolve Param's default value

[Jan Tvrdík]

Similar to already fixed #188 and #360, it would be useful if Param::$default was resolved in resolveSignature as it may contain e.g. ClassConstFetch.

[Nikita Popov]

This requires arbitrary recursion -- which is the whole point of using a visitor in the first place. If you need this, run name resolution first, without interleaving with other visitors.