[foreign] RFR: Port clang-ffi source code to new API

[Henry Jen]

Hi,

Please review the webrev[1] to allow build clang-ffi source code with foreign branch. The test still fail as jextract cannot handle libclang header file, we will address that in upcoming fixes.

The patch include NativeTypes for ABI-dependent C types, which I think is right idea but we may have different idea on how to implement that. But for now, stick into ABI make it clear that those types size is ABI dependent.

The change to adapt new pointer API is relative small. The get() seems less accurate than deref(), as it feels to get or set the address for me instead of the value pointed to. But there is always bike shed opportunity before release. :)

[1] http://cr.openjdk.java.net/~henryjen/panama/foreign/jclang-ffi/webrev/

Cheers,
Henry