Redesign how stylistic sets for particular chips work

Redesign how stylistic sets for particular chips work

The old approach was that each stylistic set had a distinct glyph-name
suffix, the same way that small caps or right-to-left mirrored glyphs
did. This meant that when several chips used the same alternative
glyph, there needed to be a separate alias for each chip.  This was
slightly awkward for just the SAA5051 and SAA5052, but I'd like to add
coverage for the SN74S262 and SN74S263, and those share some of the
same glyphs as well.

So now those stylistic sets have an explicit list of which variant
glyphs they include, and my plan is that each variant glyph will have
a single canonical name.  They'll still have to keep the existing
names for compatibility.  Indeed, for now that's what they're using
because that makes checking the output easier.

No change to the resulting font, though the lookups do end up in a
different order in the TTX file.