[vectorIntrinsics] RFR: x86 intrinsics for zero extension casts [v3]

[Mai Đặng Quân Anh]

> This patch implements the zero extension intrinsics for x86. I also fix the bug with the previous implementation where the sign elimination mask is calculated incorrectly and add several tests for this operation. I hope this will be useful.
> 
> Thank you very much.

Mai Đặng Quân Anh has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:

 - fix mistaken is_unsigned parameter
 - Merge branch 'vectorIntrinsics' into unsignedCastIntrinsics
 - renumber vector operations
 - vector unsigned cast intrinsics

-------------

Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/155/files
  - new: https://git.openjdk.java.net/panama-vector/pull/155/files/e97e68e1..ddbb76d8

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=155&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=155&range=01-02

  Stats: 916307 lines in 2434 files changed: 473164 ins; 434058 del; 9085 mod
  Patch: https://git.openjdk.java.net/panama-vector/pull/155.diff
  Fetch: git fetch https://git.openjdk.java.net/panama-vector pull/155/head:pull/155

PR: https://git.openjdk.java.net/panama-vector/pull/155