RFR: 8257234 : Add gz option to SA jmap to write a gzipped heap dump

[Lin Zang]

8257234 : Add gz option to SA jmap to write a gzipped heap dump

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Commit messages:
 - 8257234 : Add gz option to SA jmap to write a gzipped heap dump

Changes: https://git.openjdk.java.net/jdk/pull/1712/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1712&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257234
  Stats: 327 lines in 4 files changed: 292 ins; 2 del; 33 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1712.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1712/head:pull/1712

PR: https://git.openjdk.java.net/jdk/pull/1712