Fix the strangeness where typing ':' in a menu window initiated
the menu search operation but typing ':' in a text window saw
the shift key be pressed but not the ';' that went with it, even
though they both called the same key decoding routine. That made
typing ':' to initiate text search be impossible. Menu windows
did more input focus manipulation in their constructor. Mimicking
that in text windows fixes the problem with keys not being seen by
the text window's keystroke handler.
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