[foreign] jextract, distilled

[Maurizio Cimadamore]

Hi,
as we got foreign memory access and foreign function access on a much 
more solid footing --- using VarHandle and MethodHandle, respectively 
--- I thought it was time to look again at jextract and see how we could 
make these new primitives play a more central part in the extraction 
process. The writeup below captures my thinking on this topic:

http://cr.openjdk.java.net/~mcimadamore/panama/jextract_distilled.html

Cheers
Maurizio