Outright blacklist weird keys from shortcuts

I am still finding that these cause subtle problems in various places or
just do not work correctly, so we can refuse to allow them during calls
to key_event_combo().
Simplify logic for key_combo_desc()

With the blacklisting of certain keys, we do not have to attempt emulate
anything by scanning the key namespace -- this can just work with the
call to toString() with the NativeText qualifier and it will work
properly.