RFR: 8285389: EdDSA trimming zeros

[Anthony Scarpino]

Hi,

I'd like a code review of this change to EdDSA. ed25519 and ed448 internally was trimming extra zeros off the end of the signature before processing. This can result in some verify testing failures which are strict about the signature length passed into the operation. 

thanks

Tony

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Commit messages:
 - verify length

Changes: https://git.openjdk.java.net/jdk/pull/8372/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8372&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8285389
  Stats: 6 lines in 1 file changed: 5 ins; 0 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8372.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8372/head:pull/8372

PR: https://git.openjdk.java.net/jdk/pull/8372