|- Reimplement persistence logic using precise allocation rather than memory pools. This reduces
memory usage of cache entries, especially for small values, and improves performance of persisting
and unpersisting values.
- Fixed GH #335: Stampede protection is broken.
- Fixed GH #328: Segfault in apcu_key_info() if APCu is disabled.
- Generally make the behavior of functions if APCu is disabled more consistent.
- Fixed PHP bug #72980: Empty strings are now consistently allowed as cache keys.
- Optimized apcu_key_info() and apcu_cache_info() by using interned strings.
- Fix build against PHP master (PHP 7.4).
- Many changes to internal C APIs.