Poll: selection behavior in listener.

Hi All,

The TXR Interactive listener has a nil default value for *listener-sel-inclusive-p*. This makes selections work well with I-beam or vertical bar cursors.

I suspect most terminals default to a block cursor, though. The Vim editor's visual selection behavior is hard-coded to that.

Poll: should we change the default to t? The current default is confusing with a block cursors because an endpoint character that looks included in the selection actually isn't.