Log Message:
atkmm: updated to 2.28.2

atkmm 2.28.2 (stable):

Build:
* Meson build: Use relative paths to untracked/
* atkmmconfig.h.*: Don't dllimport on MinGW
* Meson build: Make it possible to use atkmm as a subproject
* Meson build: No implicit_include_directories