[HVAR/VVAR] >64k expansion; discussion

[behdad]

That was already done, thanks to the work in googlefonts/colr-gradients-spec#319

The way we did it there, there will be a chance of misinterpretting the data by an old interpretter, of a new font if it's variable, has >64k glyphs, uses a VarIdxMap (aka DeltaSetIndexMap).

At the time I was convinced this was not a big deal. I still think it's okay. After all, we're used to newer fonts not working on older implementations. That they are not misinterpretted was always a nice touch, but ultimately a useless features.

[behdad]

Nothing needs to be done.