libpng: update to 1.6.38
libpng: update to 1.6.38

oscarfv/MINGW-packages,oscarfv/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,JPeterMugaas/MINGW-packages,stahta01/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,lhmouse/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,JPeterMugaas/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,JPeterMugaas/MINGW-packages,stahta01/MINGW-packages,oscarfv/MINGW-packages,JPeterMugaas/MINGW-packages,lhmouse/MINGW-packages,lhmouse/MINGW-packages,JPeterMugaas/MINGW-packages,stahta01/MINGW-packages,lhmouse/MINGW-packages,lhmouse/MINGW-packages