RFR: 8275007: Java fails to start with null charset if LC_ALL is set to certain locales [v2]

[Naoto Sato]

> Please review the subject fix. In light of JEP400, Java runtime can/should start in UTF-8 charset if the underlying native encoding is not supported.

Naoto Sato has updated the pull request incrementally with one additional commit since the last revision:

  Emit a warning on unsupported jnu encoding

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6282/files
  - new: https://git.openjdk.java.net/jdk/pull/6282/files/0b9f6df3..d3c240c9

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6282&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6282&range=00-01

  Stats: 15 lines in 1 file changed: 15 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6282.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6282/head:pull/6282

PR: https://git.openjdk.java.net/jdk/pull/6282