Release v0.16.0

• Accessor.dummy

  • Represents a value that is never present
  • get_option dummy always returns None
  • map dummy is always a no-op

• Accessor.disjoint_field_product

  • Combines two field accessors into one accessing both inner values at once
  • Requires input accessors to access disjoint parts of the outer structure

• Accessor.disjoint_merge

  • Combines two many accessors into one accessing each inner value accessed by each accessor
  • Requires input accessors to access disjoint parts of the outer structure
• Add hash derivation to the definition of 'a Accessor.Index.t