Version 5.1.23

• Revert use of monotonic clock for TTL (#451)
• Fix a crash when serializing packed arrays (e.g. lists) in PHP 8.2+ with apc.serializer=default.
• Reduce memory usage when serializing packed arrays (e.g. lists) in PHP 8.2+ with apc.serializer=default.
• Speed up serializing arrays with apc.serializer=default.
• Reduce memory usage when unserializing instances of the empty array in PHP 7.3+.
• Removed no longer working apcue extension.
• Increased limit on maximum number of slots.
• Made tests compatible with PHP 8.3.