## Changed
- Replace `Zeroizing`'s derived `Debug` with opaque impl (#1497)

## Removed
- Internal use of `optimization_barrier` (#1535)

## Fixed
- Avoid double-zeroizing `Vec`'s initialized elements (#1525)
- False positive failures in proxy allocator test (#1538)
- Potential uninitialized memory read in fallback code used by
  `optimization_barrier` (#1551)