git: openjdk/jdk11u: 8372534: Update Libpng to 1.6.51

[Andrew John Hughes]

Changeset: be7966c6
Branch: master
Author:    Andrew John Hughes <andrew at openjdk.org>
Date:      2025-12-26 21:31:40 +0000
URL:       https://git.openjdk.org/jdk11u/commit/be7966c633830516c703f14610e4fef1bbe7f57d

8372534: Update Libpng to 1.6.51

Backport-of: 86a5a83bef9fea1e00ba4cbc9878c02e20097bec

! src/java.desktop/share/legal/libpng.md
! src/java.desktop/share/native/libsplashscreen/libpng/CHANGES
! 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/pngdebug.h
! src/java.desktop/share/native/libsplashscreen/libpng/pngerror.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngget.c
! src/java.desktop/share/native/libsplashscreen/libpng/pnginfo.h
! src/java.desktop/share/native/libsplashscreen/libpng/pnglibconf.h
! src/java.desktop/share/native/libsplashscreen/libpng/pngmem.c
! src/java.desktop/share/native/libsplashscreen/libpng/pngpread.c
! 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/pngrio.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