v6.4.0

The quality release. No code change is needed and nothing on disk moves: the data directory opens in both directions, and a 6.3.0 node pairs with a 6.4.0 node in either role — both checked against the published 6.3.0 binary.

Fixing real defects changed five answers, each measured against 6.3.0:

• GEOSEARCH / GEORADIUS above about 66° latitude returns members inside the radius it used to drop
• used_memory counts the spare capacity of strings grown by APPEND
• @now±N mo / @now±N y bounds too large to represent are refused rather than answered
• a capturing alternation in regexp_* ((a|ab)c) retries its branches
• on io_uring, a disconnect the server decides on (CLIENT KILL, buffer limits) reaches the client

Plus blocked_clients in INFO clients, a new INFO allocator, and three Rust-embedder inputs (kevy-seg, kevy-ring, kevy-time) that corrupted or panicked and are now refused or saturated.

• Upgrading: docs/upgrading-6.3-to-6.4.md · kevy.golia.jp/docs/upgrading-6.3-to-6.4 (also in Chinese and Japanese)
• Everything else: CHANGELOG

Full Changelog: v6.3.0...v6.4.0