RFR: 4890732: GZIPOutputStream doesn't support, in fact thwarts, use of optional GZIP fields

[Lin Zang]

4890732: GZIPOutputStream doesn't support, in fact thwarts, use of optional GZIP fields

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Commit messages:
 - remove trailing spaces
 - 4890732: support optional GZIP fields in GZIPOutputStream

Changes: https://git.openjdk.java.net/jdk/pull/3072/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3072&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-4890732
  Stats: 184 lines in 1 file changed: 184 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3072.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3072/head:pull/3072

PR: https://git.openjdk.java.net/jdk/pull/3072