Vector API - Support for Double128, Double256 and Int256 datatypes

[Rukmannagari, Shravya]

Hi Everyone,
This is Shravya Rukmannagari, Software Engineer at Intel and I recently started working with Ian Graves on the VectorAPI project. This is my first contribution to Panama-dev which adds support to Double128, Double256 and Int256 types.
http://cr.openjdk.java.net/~igraves/webrev-shravya1/

Thanks!

Best Regards,
Shravya Rukmannagari.