Update libpng16 to version 1.6.39 / rev 47 via SR 1038197
https://build.opensuse.org/request/show/1038197
by user pgajdos + dimstar_suse
- Update to version 1.6.39:
* cmake: Default to PNG_ARM_NEON=off for arm targets.
+ Turn large PNG chunks into benign errors.
+ Update, rename and clean up various scripts.
+ tools: Fix a buffer overflow involving a file name in pngfix.
+ tools: Fix a memory leak in pngcp. (forwarded request 1038184 from dimstar)