Upgrade UBB.threads from a previous version

Version checks:
• Current database structure version: 8.0.0
• Script version reported by database: 8.0.0
• Script version on filesystem: 8.0.0 Preview 20240506

Continuing will perform the following tasks:
• Upgrade your current version of UBB.threads to UBB.threads 8.0.0 Preview.
• Retain your current forum threads, posts, users and other information.