input: bind key bindings to raw key codes too

Before, when looking for a matching user key binding, we only
matched *symbols*.

This means that the physical keys that generate a specific key binding
is layout dependent. What's worse, it may not even be possible to
generate the key binding at all.

Russian is one such layout, where all the "normal" (us) symbols are
replaced.

By using raw key codes, we can get around this - the key code has a
direct mapping to the physical key.

However, matching raw key codes **only** doesn't always make sense
either. For now, match **both** symbols _and_ key codes. Symbols take
precedence.

TODO: we might have to make this configurable _per binding_.

Note: 'search' mode still uses mostly hardcoded shortcuts that still
have this problem (i.e. ctrl+g doesn't work with a russian layout).

wayland.h

@@ -84,9 +84,12 @@ enum binding_action {
     BIND_ACTION_COUNT,
 };
 
+typedef tll(xkb_keycode_t) xkb_keycode_list_t;
+
 struct key_binding {
     xkb_mod_mask_t mods;
     xkb_keysym_t sym;
+    xkb_keycode_list_t key_codes;
     enum binding_action action;
 };
 typedef tll(struct key_binding) key_binding_list_t;