This is an incompatible change to the plugin ABI.
The Console is not thread-safe unless used indirectly
via color_ostream_proxy, so everything should use their
per-thread stream.
Units can be selected via 'u', 'j', 'v' and 'k'; full-screen
unit details view not supported.
Items can be selected via 't', 'k', 'v'->inventory.
Also, when viewing a container item full-screen, the selected
contained item or unit is returned; never the container itself.
The api is used in rename to allow setting nicknames for
arbitrary units, including animals and enemies.