swift234

Don't add names to non-resolvable scopes

Currently not only we insert names in non-resolvable scopes, but every
overloaded name gets stored only once (the last one wins).  Everything just
happens to work, because we never do name lookup in these scopes.

I also added a ScopeKind to every Scope (instead of just adding the bit --
isResolvableScope), because this provides a better debugging experience, and
centralizes knowledge about what scope kind is resolvable in the function
isResolvableScope(ScopeKind).


Swift SVN r5822