[jdk8u-dev] RFR: Merge jdk8u:master

[Andrew John Hughes]

Merge jdk8u482-b07 back into 8u-dev

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Commit messages:
 - Merge jdk8u:master
 - 8372534: Update Libpng to 1.6.51

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.org/jdk8u-dev/pull/743/files
  Stats: 6267 lines in 23 files changed: 2572 ins; 2571 del; 1124 mod
  Patch: https://git.openjdk.org/jdk8u-dev/pull/743.diff
  Fetch: git fetch https://git.openjdk.org/jdk8u-dev.git pull/743/head:pull/743

PR: https://git.openjdk.org/jdk8u-dev/pull/743