Add declaration of g_error_new_valist().

Signed-off-by: Andrew Borodin <aborodin@vmail.ru>

lib/glibcompat.h

@@ -19,6 +19,10 @@ gboolean g_unichar_iszerowidth (gunichar);
 int g_strcmp0 (const char *str1, const char *str2);
 #endif /* ! GLIB_CHECK_VERSION (2, 16, 0) */
 
+#if ! GLIB_CHECK_VERSION (2, 22, 0)
+GError * g_error_new_valist (GQuark domain, gint code, const gchar * format, va_list args);
+#endif /* ! GLIB_CHECK_VERSION (2, 22, 0) */
+
 #if ! GLIB_CHECK_VERSION (2, 28, 0)
 void g_slist_free_full (GSList * list, GDestroyNotify free_func);
 void g_list_free_full (GList * list, GDestroyNotify free_func);