Merge tag 'v1.6.58' into libpng18
Release libpng version 1.6.58
chore: Update .gitignore to exclude the recently-added test program
test: Ensure the palette sync follows the gamma correction
fix: Sync `info_ptr->palette` unconditionally after in-place transforms
Bump version to 1.6.58.git
fix: Consume chunk body in APNG push-mode discard paths
Merge tag 'v1.6.57' into branch 'libpng18' into develop