#3 duplicate tab completetions (and more)

[Bernhard Ege]

When pressing tab repeatedly, words from the putput
history are inserted multiple times. The reason seems
to be because the tab completion display is included
in the word search for the tab completions.

This has a side effect: The tab completions are are
written in one long string without linebreak. The
longer the completion list, the more it slows down
the display of SMM. And it can get very slow.