Log Message:
harfbuzz: update to 4.2.0.

Overview of changes leading to 4.2.0
Wednesday, March 30, 2022
====================================
- Source code reorganization, splitting large hb-ot-layout files into smaller,
  per-subtable ones under OT/Layout/*. Code for more tables will follow suit in
  later releases. (Garret Rieger, Behdad Esfahbod)
- Revert Indic shaper change in previous release that broke some fonts and
  instead make per-syllable restriction of “GSUB” application limited to
  script-specific Indic features, while applying them and discretionary
  features in one go. (Behdad Esfahbod)
- Fix decoding of private in gvar table. (Behdad Esfahbod)
- Fix handling of contextual lookups that delete too many glyphs. (Behdad Esfahbod)
- Make “morx” deleted glyphs don’t block “GPOS” application. (Behdad \ 
Esfahbod)
- Various build fixes. (Chun-wei Fan, Khaled Hosny)

- New API
+hb_set_next_many() (Andrew John)