Updated png++ libs

_tools/code_generators/libs/png++/ChangeLog

_tools/code_generators/libs/png++/Doxyfile

_tools/code_generators/libs/png++/Makefile

_tools/code_generators/libs/png++/NEWS

_tools/code_generators/libs/png++/common.mk

_tools/code_generators/libs/png++/config.hpp

_tools/code_generators/libs/png++/consumer.hpp

_tools/code_generators/libs/png++/convert_color_space.hpp

_tools/code_generators/libs/png++/error.hpp

_tools/code_generators/libs/png++/example/Makefile

_tools/code_generators/libs/png++/generator.hpp

_tools/code_generators/libs/png++/gray_pixel.hpp

_tools/code_generators/libs/png++/image.hpp

_tools/code_generators/libs/png++/image_info.hpp

_tools/code_generators/libs/png++/index_pixel.hpp

_tools/code_generators/libs/png++/info.hpp

_tools/code_generators/libs/png++/io_base.hpp

_tools/code_generators/libs/png++/packed_pixel.hpp

_tools/code_generators/libs/png++/pixel_buffer.hpp

_tools/code_generators/libs/png++/pixel_traits.hpp