Make AttackerGenerator noncopyable.
Reindent AttackerGenerator.
Constify AttackerGenerator.
Constify PseudoLegalMoveGenerator.
Make PseudoLegalMoveGenerator immutable.
Make AttackerGenerator immutable.
Reindent PseudoLegalMoveGenerator.
Reindent LegalMoveGenerator.
Fix return value policies.
Cleanup PolyglotOpeningBookEntry.
Add copy constructor for Polyglot entries.