• Fix regression since 4.5.0 where key tracking for components would fail in some cases, causing components not to be recycled. Relates to #98 and the second issue noted in #120.
• Switch to a global/named symbol Symbol.for('preactattr') for the prop cache key (still falling back to __preactattr_).
• Address the state re-use issue noted in Issue #120 by manually re-invoking component constructors when re-using components from the recycler.