[vectorIntrinsics] RFR: x86 intrinsics for zero extension casts [v2]

[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 incrementally with one additional commit since the last revision:

  renumber vector operations

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Changes:
  - all: https://git.openjdk.java.net/panama-vector/pull/155/files
  - new: https://git.openjdk.java.net/panama-vector/pull/155/files/0365b4a9..e97e68e1

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=155&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=panama-vector&pr=155&range=00-01

  Stats: 16 lines in 2 files changed: 0 ins; 0 del; 16 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