RFR: JDK-8316030: Update Libpng to 1.6.40

[Harshitha Onkar]

On Thu, 19 Oct 2023 16:11:41 GMT, Damon Nguyen <dnguyen at openjdk.org> wrote:

>> Libpng updated from 1.6.39 to 1.6.40
>> 
>> Build and CI Testing passes on all platforms.
>
> src/java.desktop/share/native/libsplashscreen/libpng/pngget.c line 60:
> 
>> 58:       if (flag == PNG_INFO_tRNS && png_ptr->num_trans == 0)
>> 59:          return(0);
>> 60: #endif
> 
> What's this addition doing exactly?

This is an upstream issue. 
Details about the issue and fix is available on libpng source repo.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16223#discussion_r1367320826