Log Message:
Update harfbuzz to 2.3.0.

-   Fix regression on big-endian architectures. Ouch!
-   Misc bug and build fixes.
-   Fix subsetting of simple GSUB/GDEF.
-   Merge CFF / CFF2 support contributed by Adobe. This mostly involves
    the subsetter, but also get_glyph_extents on CFF fonts.