If g-p is a builtin binding and p is bound in input.conf, pressing g-p
triggers the p binding. Fix this by searching for builtin bindings that
match a longer key sequence even after a user-defined binding has been
found.
Even after changing the condition from >= to > bindings of the same key
defined later in input.conf are still preferred over earlier ones,
because bind_keys() overwrites duplicate bindings. Bindings defined by
later mp.add_key_binding calls are also still preferred.