AGS 4: deprecate ASCII text mode in games

[ivan-mogilko]

The proposal is to deprecate ASCII / ANSI text mode, and have strictly Unicode (UTF-8) mode in games.
ASCII is too restrictive. Removing ASCII mode will simplify engine code, and reduce accidental confusion when user chose wrong text mode.

The only known downside of not having it is related to WFN fonts: there's simply not a lot of available Unicode-compatible WFNs around (if any at all). Whether this is too serious issue to cut ASCII mode completely remains a question. If it is, then this may be postponed until there are better tools around.

Likely we'll have to provide updated bitmap font editors that can assign glyphs into unicode indexes (e.g. see updated FontEdit).
Perhaps, it will be quite worth to have a tool that automatically converts a ANSI-compatible WFN into Unicode-compatible, simply by moving glyphs to new indexes (except it will need to know original ANSI code page).

EDIT: another potential issue is SpriteFont plugin. I don't remember how it manages glyph indexes, but if it's similar to WFN, then it will have same trouble and will require updating as well.