[jdk8u] Integrated: 8372534: Update Libpng to 1.6.51

[Andrew John Hughes]

On Sat, 27 Dec 2025 18:26:18 GMT, Andrew John Hughes <andrew at openjdk.org> wrote:

> Update to the latest version of libpng. Change includes both the backport of the latest libpng change, [JDK-8372534](https://bugs.openjdk.org/browse/JDK-8372534), and previous updates not present in 8u ([JDK-8316030](https://bugs.openjdk.org/browse/JDK-8316030) - 1.6.40, [JDK-8329004](https://bugs.openjdk.org/browse/JDK-8329004) - 1.6.43, [JDK-8348598](https://bugs.openjdk.org/browse/JDK-8348598) - 1.6.47). The change built fine with GCC 8 on RHEL 8 and `java/awt/SplashScreen` tests passed.
> 
> I also included `UPDATING.txt` introduced in [JDK-8208353](https://bugs.openjdk.org/browse/JDK-8208353) in 11u, but not 8u, and updated in [JDK-8295685](https://bugs.openjdk.org/browse/JDK-8295685) as part of the JDK-8329004 backport which updates it.
> 
> I'm proposing this during rampdown so the release ships with the latest version, as we also do with e.g. tzdata.

This pull request has now been integrated.

Changeset: 976d0a19
Author:    Andrew John Hughes <andrew at openjdk.org>
URL:       https://git.openjdk.org/jdk8u/commit/976d0a196ce036c40147535209b80143e021c2fe
Stats:     6267 lines in 23 files changed: 2572 ins; 2571 del; 1124 mod

8372534: Update Libpng to 1.6.51
8316030: Update Libpng to 1.6.40
8329004: Update Libpng to 1.6.43
8348598: Update Libpng to 1.6.47

Reviewed-by: abakhtin, serb
Backport-of: be7966c633830516c703f14610e4fef1bbe7f57d

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PR: https://git.openjdk.org/jdk8u/pull/83