maxp.maxZones == 0 causes ots warning

[justvanrossum]

TBH I'm not sure who's wrong or right here, just wanted to put this out here as an observation.

https://github.com/khaledhosny/ots/blob/ff09cd0b6b0dd210a4c1bafd61fcbbba21738751/src/maxp.cc#L50

The workaround is to call dehinter with --keep-maxp.

[anthrotype]

It should be set to 1 for unhinted I think (they don't use the 'twilight zone')

https://docs.microsoft.com/en-us/typography/opentype/spec/maxp