RFR: 8277398: javac does not accept encoding name COMPAT

[Ichiroh Takiguchi]

ncoding name COMPAT was defined for operating system encoding by JEP-400.
https://openjdk.java.net/jeps/400
But java does not accept "-encoding COMPAT".

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Commit messages:
 - 8277398: javac does not accept encoding name COMPAT

Changes: https://git.openjdk.java.net/jdk/pull/6475/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=6475&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8277398
  Stats: 109 lines in 3 files changed: 106 ins; 0 del; 3 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6475.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6475/head:pull/6475

PR: https://git.openjdk.java.net/jdk/pull/6475