validations. We now have an open ledger, a last closed ledger, and a last
validated ledger. Normally, a ledger will be validated right after it
closes, but in edge cases, we might see a ledger close that then doesn't get
validated. This makes the code do the right thing.
Most of these fixes involve calls to BOOST_FOREACH to iterate over a map or unordered_map where the
iterator type didn't perfectly match the internal type, so a reference into the map couldn't be created
and a new value/content pair had to be created for each iteration.
