This update for libpng16 fixes the following issues:
png_image_read_composite via
incorrect palette premultiplication (bsc#1254159)png_do_quantize via
malformed palette index (bsc#1254157)png_write_image_8bit
with 8-bit input and convert_to_8bit enabled (bsc#1254158)png_combine_row
triggered via png_image_finish_read (bsc#1254160)1.6.8-15.9.11.6.8-15.9.11.6.8-15.9.11.6.8-15.9.11.6.8-15.9.1