git: openjdk/jdk17u-dev: 8295685: Update Libpng to 1.6.38

[Goetz Lindenmaier]

Changeset: 62ccb396
Author:    Goetz Lindenmaier <goetz at openjdk.org>
Date:      2023-01-25 08:47:10 +0000
URL:       https://git.openjdk.org/jdk17u-dev/commit/62ccb3967bfa9b7a34e62cd6cc376c289ec024c8

8295685: Update Libpng to 1.6.38

Backport-of: b685fc2de4d2847de2d1efaab2890646257ea6d3

! 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/UPDATING.txt
! 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/pngget.c
! 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/pngread.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngrtran.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngrutil.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngset.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngstruct.h