v0.1008.0

v0.1008.0

Breaking changes

• The (unstable) internal encoding traits continue to evolve, now making checks
  for whether a value decoded in distinguished mode was empty optional at the
  value-decoder trait level. It is not always faster to check emptiness while
  decoding a value, and letting the distinguished value decoder implementation
  specify whether it takes responsibility for checking emptiness enables new
  type support like better nesting of never-empty types as described below.

Fixes

• Enumerations that do not have a defined zero value (and therefore do not have
  an "empty" state) can now be nested in fixed-size arrays as long as they are
  nested again, such as in an Option or Vec.

Cleanups

• Renamed the NewForOverwrite value trait to ForOverwrite.
• Restructured so that ForOverwrite is now a supertrait of EmptyState, and
  every existing implementation of EmptyState::empty defers to ForOverwrite.