[foreign] RFR: 8208063 Jextract should generate empty interface for undefined/opaque record type

[Henry Jen]

Hi,

Please review the webrev[1] that create empty interface for undefined struct, this was discussed not too long ago, and we decided the layout type should be Unresolved instead of unknown number of bytes.

Cheers,
Henry

[1] http://cr.openjdk.java.net/~henryjen/panama/UndefinedStructAsInterface/webrev/