Methods:
- DefaultIfEmpty

Classes:
- LINQ::DBI
- LINQ::LibXML

Optimization:
- LINQ::Iterator->select
- LINQ::Iterator->where
- LINQ::Iterator->select_many
- LINQ::Iterator->element_at
- LINQ::Iterator->first
- LINQ::Iterator->zip
- LINQ::Collection->any

Features:
- LINQ::Collection->to_array ought to return a tied array pointing back to the collection
