Update to libpng 1.6.45?

[Neustradamus]

Dear @winlibs team, @cmb69, @weltling,

Have you planned an update?

• https://github.com/pnggroup/libpng/tags

Thanks in advance.

[cmb69]

From http://www.libpng.org/pub/png/libpng.html:

The current public release, libpng 1.6.45, includes minor fixes and improvements:

So not urgent in any way, but may be a good idea nonetheless.