Right now, we use XLookupString () instead; this is sort
of useful because it gives us the string that we have in
the GdkEvent (but we don't use that string anywhere, and
shouldn't -- string translations come from the input method).

However, we are basically just hoping that XLookupString()
is consistent with what we do in gdk_keymap_translate_keyboard_state -
that better be true in broad outline anyways so that GDK apps
work like other apps, but in some parts ... e.g., the fudging
of GDK_Tab / GDK_ISO_Left_Tab, we are already deviating
a bit.