Initial import. Most things seem working.

This includes an abortive attempt to do a gtk4 dialog (which I don't
think is possible, as gtk4 doesn't allow embedding toplevels anymore),
and an iced dialog, which I just never started writing.

dialog-gtk3/Cargo.toml

@@ -0,0 +1,18 @@
+[package]
+name = "bscreensaver-dialog-gtk3"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+anyhow = "1"
+bscreensaver-util = { path = "../util" }
+chrono = "0.4"
+gethostname = "0.2"
+glib = { version = "0.15", features = ["v2_68"] }
+gtk = { version = "0.15", features = ["v3_24"] }
+gtk-sys = "0.15"
+gdk-sys = "0.15"
+gdkx11 = "0.15"
+log = "0.4"
+pam = "0.7"
+#x11 = "2.19"