RFR: 8256995: [vector] Improve broadcast operations

[Paul Sandoz]

Use the raw FP to bits conversion methods (to avoid NaN checks). Improve the x64 code generation when broadcasting a value.

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Commit messages:
 - Update to support all replicate patterns.
 - Improve IntVector.broadcast on x64 platforms.
 - Use raw bit conversions for FP values.

Changes: https://git.openjdk.java.net/jdk/pull/1445/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1445&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8256995
  Stats: 20 lines in 4 files changed: 17 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1445.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1445/head:pull/1445

PR: https://git.openjdk.java.net/jdk/pull/1445