Major feature: Classic Support!

BigChatBox now works in TBC Anniversary, Mists of Pandaria Classic, and Vanilla Classic Era!

• One addon, all versions. The same editbox, snippets, history, autocomplete, and config window you know from Midnight
• Classic clients use a compatibility layer that handles API differences transparently, so no separate addon to install
• The config window sliders are built from scratch to look as close to retail as it can be in Classic, using only universally available primitives
• Language override is a retail-only feature (requires a Midnight TOC directive). Classic uses your client locale automatically
• Multiline box is currently retail-only and will come to Classic in a future update
• All other previous features from v5.7.6 carry over
• Considering that classic version aren't as restrictive with their APIs, maybe some features that don't work with Midnight will make it to these versions

 This is the first release candidate, so it might be a bit buggy in the classic clients. Retail will be the same.