#11 Tab completion maintains state across windows

[Tara McGrew]

Join two channels. In channel 1, type the first letter
of a nick and press TAB to complete it. Switch to
channel 2 and press TAB without typing any letters.
Notice that all nicks are highlighted, and completion
proceeds with nicks from channel 1 - only the first
nick should be highlighted, and completion should start
with the first nick from channel 2.