[jdk8u-dev] RFR: 8305815: Update Libpng to 1.6.39

[Paul Hohensee]

On Thu, 14 Sep 2023 20:44:35 GMT, Martin Balao <mbalao at openjdk.org> wrote:

> Hi all,
> 
> This pull request contains a backport of commit [c1f759e9d01d646eac69442452151b0467eab306](https://github.com/openjdk/jdk11u-dev/commit/c1f759e9d01d646eac69442452151b0467eab306) from the [openjdk/jdk11u-dev](https://github.com/openjdk/jdk11u-dev) repository.
> 
> This backport is a follow up fix of [JDK-8295685](https://bugs.openjdk.org/browse/JDK-8295685).
> 
> This backport applied cleanly, except for the changes to the THIRD_PARTY_README files that are specific to 8u.
> 
> Thanks!

Marked as reviewed by phh (Reviewer).

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PR Review: https://git.openjdk.org/jdk8u-dev/pull/373#pullrequestreview-1629409755