Log Message:
glibmm: updated to 2.66.1

2.66.1 (stable):

Glib:
* Variant: Fix template constructors so they work with C++20

Build:
* Meson build: Use relative paths to untracked/
* MSVC build: Export Glib::manage()
* [gio|glib]mmconfig.h.*: Don't dllimport on MinGW
* Meson build: examples and tests: Add dependency('threads')
* Meson build: Make it possible to use glibmm as a subproject
* Meson build: No implicit_include_directories
* Meson build: Make quiet installations possible
* MSVC build: Avoid exporting classes with std::string members