[vector] concrete shuffle

[Paul Sandoz]

Hi,

In the same manner as the mask implementation was updated to have concrete types per element type and shape this patch does the same for shuffle:

  http://cr.openjdk.java.net/~psandoz/panama/concrete-shuffle/webrev/index.html <http://cr.openjdk.java.net/~psandoz/panama/concrete-shuffle/webrev/index.html>

This is based off the patch for species reshape/cast.

Thanks,
Paul.