The fixes are already in upstream repository, but as both games herd and I already noticed (in case of sdl-sound), it's hard to tell when the release will happen.
Created attachment 262563 [details, diff]
This is the patch I added to my private overlay for testing libpng-1.5.x. It's simply a diff between latest IMG_png.c file from their VCS and the one from 1.2.10 release.
Thanks for report and patch.