Various recompilation errors

I wrote this test program to recompile all tables of a font: https://gist.github.com/madig/221321d2343bfc3f4531511067d6be04.

It does not try all the tables because they don't seem to have `to_owned_table()` and I haven't yet figured out what to do about it.

Run like:

```fish
$ for f in /usr/share/fonts/**/*.ttf
target/release/mess-with-ot $f
end
```

It finds various errors like:

```
Reading font from: "/usr/share/fonts/google-noto-vf/NotoSans-Italic[wght].ttf"
thread 'main' panicked at src/main.rs:162:14:
Cannot compile table: BuilderError { tag: Tag(GPOS), inner: PackingFailed(Table packing failed with 21 overflows) }

Reading font from: "/usr/share/fonts/google-noto-vf/NotoSans[wght].ttf"
thread 'main' panicked at src/main.rs:162:14:
Cannot compile table: BuilderError { tag: Tag(GPOS), inner: PackingFailed(Table packing failed with 54 overflows) }

Reading font from: "/usr/share/fonts/google-noto-vf/NotoSansEthiopic[wght].ttf"
thread 'main' panicked at src/main.rs:162:14:
Cannot compile table: BuilderError { tag: Tag(GPOS), inner: PackingFailed(Table packing failed with 16592 overflows) }

Reading font from: "/usr/share/fonts/google-noto-vf/NotoSerif-Italic[wght].ttf"
thread 'main' panicked at src/main.rs:162:14:
Cannot compile table: BuilderError { tag: Tag(GPOS), inner: PackingFailed(Table packing failed with 61 overflows) }

Reading font from: "/usr/share/fonts/google-noto-vf/NotoSerif[wght].ttf"
thread 'main' panicked at src/main.rs:162:14:
Cannot compile table: BuilderError { tag: Tag(GPOS), inner: PackingFailed(Table packing failed with 68 overflows) }

Reading font from: "/usr/share/fonts/khmer-os-system-fonts/KhmerOS_sys.ttf"
thread 'main' panicked at src/main.rs:42:14:
Cannot compile table: BuilderError { tag: Tag(name), inner: ValidationFailed(Validation error:
"Unhandled platform/encoding id pair: (1, 20)"
in: Name.name_record[16]
NameRecord.string

) }
```

Start with the linked test program and reproduce the failures using the fish loop over the installed TTF files. Inspect the panic at src/main.rs:162 and compare the GPOS packing failures with the name-table validation error. Done means the reported recompilation errors are understood and the affected tables can be recompiled successfully.

Written by the indexing model from the issue text.