- Adds vdup.<size> Dd/Qd, Dm[i] instruction.
- Adds vsli, vsri instructions.
- Changes VMovExtended to use these to avoid moves to core registers.

LOG=N
BUG=v8:6020

Review-Url: https://codereview.chromium.org/2868603002
Cr-Commit-Position: refs/heads/master@{#45351}