fix misleading FullBox parameters

[fcartegnie]

FullBox as defined by ISO14496-12 has 8+24bits for versioning and flags. Passing both 32bits integers for those params is misleading and will anyway be truncated.

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[fcartegnie]

I signed it!

[googlebot]

CLAs look good, thanks!

[dcower]

Thanks, Francois! LGTM. Passing this on to Aaron to double check. :)