Log Message:
glibmm: updated to 2.66.6

2.66.6 (stable):

Glib:
* Dispatcher: Don't warn when a Dispatcher is deleted while
  messages are pending.

Gio:
* NetworkMonitor::get_default(): Add refreturn

gmmproc:
* generate_wrap_init.pl.in: Disable warning C4273 on Visual Studio

Meson build:
* Detect if we build from a git subtree
* Don't copy files with configure_file()