s2 cannot handle more than 2^31 - 1 vertices in polyline/polygon

[MBkkt]

https://github.com/google/s2geometry/blob/master/src/s2/encoded_s2point_vector.h#L131

Access by int, uint32 size_, by size encoded and decoded as size_t

So in general s2 cannot handle more than 2^31 - 1 vertices in polyline/polygon :(

It looks pretty easy to fix and also looks like current encoding/decoding can handle this.

Do you plan to fix this?