git: openjdk/jdk17u-dev: 8305815: Update Libpng to 1.6.39

[Goetz Lindenmaier]

Changeset: 5fc07b5b
Author:    Goetz Lindenmaier <goetz at openjdk.org>
Date:      2023-06-19 07:13:22 +0000
URL:       https://git.openjdk.org/jdk17u-dev/commit/5fc07b5bd094039548b90541808e49a7277a0697

8305815: Update Libpng to 1.6.39

Backport-of: 14874779eeb9a279479c5aaddb40c056780d6152

! src/java.desktop/share/legal/libpng.md
! src/java.desktop/share/native/libsplashscreen/libpng/CHANGES
! src/java.desktop/share/native/libsplashscreen/libpng/LICENSE
! src/java.desktop/share/native/libsplashscreen/libpng/README
! src/java.desktop/share/native/libsplashscreen/libpng/png.c
! src/java.desktop/share/native/libsplashscreen/libpng/png.h
! src/java.desktop/share/native/libsplashscreen/libpng/pngconf.h
! src/java.desktop/share/native/libsplashscreen/libpng/pnglibconf.h
! src/java.desktop/share/native/libsplashscreen/libpng/pngpriv.h
! src/java.desktop/share/native/libsplashscreen/libpng/pngrutil.c