Add various gtk list models

This is an exact copy from GTK4.
as grabbed by chattys commit 1ed5084fb965908e3ee0304781b0de06479c869b

Slightly adapted for Calls.

Based on GTKs 01bd4cc4e18a1ea697fe61791ba710d0d55e8290

src/gtklistmodels/gtkintl.h

@@ -0,0 +1,22 @@
+#ifndef __GTKINTL_H__
+#define __GTKINTL_H__
+
+#ifndef GETTEXT_PACKAGE
+# define GETTEXT_PACKAGE
+#endif
+#include <glib/gi18n-lib.h>
+
+#ifndef G_GNUC_FALLTHROUGH
+#define G_GNUC_FALLTHROUGH __attribute__((fallthrough))
+#endif
+
+#ifdef ENABLE_NLS
+#define P_(String) g_dgettext(GETTEXT_PACKAGE "-properties",String)
+#else 
+#define P_(String) (String)
+#endif
+
+/* not really I18N-related, but also a string marker macro */
+#define I_(string) g_intern_static_string (string)
+
+#endif