* Remove `glib-mkenums` autotools templates and generated files
Meson uses the `enumtypes.c.in` and `enumtypes.h.in` in
`libvips/include/vips` and doesn't use the pre-generated
files.
* Remove man files for no longer existing tools
+ update the `meson.build`.
* Remove Autotools section in `.gitignore`
* Remove `po/messages` left-over
* Remove `g-ir-scanner` entry point
No longer needed by Meson.
* Remove `glib-genmarshal` generated files
Meson doesn't use these pre-generated files.
* Remove Autotools specific Git attributes
* Remove no longer existing tools in `.gitignore`
* Remove Make specific things in `.gitignore`
* Rename COPYING to LICENSE
* Remove no longer needed `.gitignore` sections
Meson only supports out-of-tree builds. This assumes that the
build directory is ignored.
* Remove no longer needed `.editorconfig` sections
