[jdk17u-dev] RFR: 8316030: Update Libpng to 1.6.40

[Goetz Lindenmaier]

I backport this for parity with 17.0.11-oracle.

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Commit messages:
 - Backport 158293d2517695f8c5eaca1b46ecf0f1f9f09691

Changes: https://git.openjdk.org/jdk17u-dev/pull/1998/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1998&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316030
  Stats: 246 lines in 11 files changed: 89 ins; 82 del; 75 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1998.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1998/head:pull/1998

PR: https://git.openjdk.org/jdk17u-dev/pull/1998