Now the development and stable logos will be generated from gimp-data.
In other changes, the gi-docgen logo is installed as a symlink using
install_symlink() which exists since meson 0.61.0 so I bumped our meson
dependency (in practice we were already using this function anyway and Debian
bookworm has meson 1.0.1 so it's all good).
Finally I don't install a wilber.png anymore, which was only used by script-fu
testing, and which was the same as gimp-logo.png (except 256x256 instead of
128x128). Unless mistaken, all script-fu tests loading this image still work
with the change. The only one where I needed further change was buffer.scm
(which was checking the dimensions).
See gimp-data@9aa6e35.
42171503d4