- kern/GPOS interaction

- Use size_t in sanitize?
- Buffer error handling?
- Better define HB_INTERNAL
- Future-proof metrics struct

hb-ot:
- Rename hb_internal_glyph_info_t to hb_ot_glyph_info_t
- Add query API for aalt-like features
- HB_OT_LAYOUT_GLYPH_CLASS_BASE_GLYPH vs LookupType::... mess