unicode_lower_table / unicode_upper_table should be deprecated

[Oreolek]

Modern JS (since circa 2014) has proper String.toLowerCase and String.toUpperCase methods and they are Unicode-aware. Quixe tables are not really Unicode-aware, they fail on non-Latin scripts.

File in question: https://github.com/erkyrath/quixe/blob/a882f4b3d7f2bbd6453a14231eaa226ec34d9b50/src/glkote/glkapi.js#L1297

[erkyrath]

I am somewhat torn between using the JS facility for Unicode or sticking with my old implementation, which will behave consistently with the C interpreters.