RFR: 8255894: Remove unused StubRoutines::_zero_aligned_words

[Claes Redestad]

_zero_aligned_words was a SPARC-only optimization added by JDK-7059037

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Commit messages:
 - Remove unused StubRoutines::_zero_aligned_words

Changes: https://git.openjdk.java.net/jdk/pull/1053/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1053&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255894
  Stats: 7 lines in 2 files changed: 0 ins; 7 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1053.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1053/head:pull/1053

PR: https://git.openjdk.java.net/jdk/pull/1053