#2891 wxt terminal run under wayland fails to show zoom box

[Ethan Merritt]

Gnuplot 6 or 6.1 running under wayland display server, as opposed to x11.
Tested using wxgtk3.2

Adding a "Refresh()" command allowed plots to display and refresh correctly without having to bypass wayland by setting GD_BACKEND=x11. However transient features, notably the zoom box, are still not displayed under wayland. These might logically be handled by adding an Update() command, but the gdk/gtk documentation for both gtk3 and gtk4 explicitly state that Update() is not implemented for the wayland backend.