optipng 7.9.1

Version 7.9.1 2025-may-20
-------------
* Upgraded libpng to version 1.6.48.
!! REALLY fixed a corner case in the RGB-to-palette reduction code,
in which a dangling tRNS chunk (i.e. a tRNS chunk containing an
RGB triplet that doesn't actually exist in the RGB-encoded image)
should have been discarded (but wasn't).
[Re-reported by Dan Fandrich]
+ Enabled the making of a SIMD-optimized build of libpng on select
target platforms. Currently, this is enabled by default on ARM64
and X86-64.
+ Added a CMake file, an alternative to the configure build script.
- Deprecated the configure build script.
- Removed the support for 16-bit platforms.
- Removed the option -log.
* Rewrote the user manual in AsciiDoc format.
** Got bored of 0-dot-version numbers.

Version 0.7.9 2025-apr-11
-------------
* Upgraded libpng to version 1.6.47.
* Upgraded zlib to version 1.3.1-optipng.
* Upgraded cexcept to version 2.99-optipng.
!! Fixed a corner case in the RGB-to-palette reduction code, in which
a dangling tRNS chunk (i.e. a tRNS chunk containing an RGB triplet
that doesn't actually exist in the RGB-encoded image) should have
been discarded (but wasn't); this caused the palette-encoded output
image to contain bogus transparency.
[Reported by Andrew Dent]