sync wityh texlive revision 44931.

source/libs/libpng/ChangeLog

source/libs/libpng/README

source/libs/libpng/TLpatches/ChangeLog

source/libs/libpng/TLpatches/TL-Changes

source/libs/libpng/configure

source/libs/libpng/libpng-src/ANNOUNCE

source/libs/libpng/libpng-src/CHANGES

source/libs/libpng/libpng-src/CMakeLists.txt

source/libs/libpng/libpng-src/INSTALL

source/libs/libpng/libpng-src/LICENSE

source/libs/libpng/libpng-src/README

source/libs/libpng/libpng-src/arm/filter_neon.S

source/libs/libpng/libpng-src/configure.ac

source/libs/libpng/libpng-src/contrib/arm-neon/linux.c

source/libs/libpng/libpng-src/contrib/libtests/pngstest.c

source/libs/libpng/libpng-src/contrib/libtests/pngunknown.c

source/libs/libpng/libpng-src/contrib/libtests/pngvalid.c

source/libs/libpng/libpng-src/contrib/testpngs/makepngs.sh

source/libs/libpng/libpng-src/contrib/tools/pngfix.c

source/libs/libpng/libpng-src/example.c