RFR: 8252842: Extend jmap to support parallel heap dump [v30]

[Lin Zang]

> 8252842: Extend jmap to support parallel heap dump

Lin Zang has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 39 commits:

 - Merge branch 'master' into par-dump
 - fix build issue
 - Merge branch 'master' into par-dump
 - Merge branch 'master' into par-dump
 - Merge branch 'master' into par-dump
 - fix build issue after rebase and fix one issue
 - Merge branch 'master'
 - Merge branch 'master' into pd
 - update copyright info
 - Merge branch 'master' into par-dump
 - ... and 29 more: https://git.openjdk.java.net/jdk/compare/d06d0b9e...5268e5d9

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Changes: https://git.openjdk.java.net/jdk/pull/2261/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=2261&range=29
  Stats: 835 lines in 5 files changed: 648 ins; 57 del; 130 mod
  Patch: https://git.openjdk.java.net/jdk/pull/2261.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/2261/head:pull/2261

PR: https://git.openjdk.java.net/jdk/pull/2261