[imp] DIMP + "delete" key

[Chuck Hagenbuch]

Quoting Liam Hoekenga <liamr at umich.edu>:

> Apparently, this breaks the ability to us the backspace key in the DIMP
> serach box on IE 6 (and other?) and Firefox 2 on WinXP, and Safari on OSX
> (when Safari works with DIMP)
>
> Strangely, the delete key on my powerbook (which sends BACKSPACE) will
> both delete messages in the DIMP index pane *and* delete text in the
> search box when I use it with Firefox 2 for OSX.

So should we just remove the BACKSPACE support? Should we consider  
another delete shortcut, like ctrl/alt-D, or just 'D' on its own?

Alternately, shouldn't be we checking e.element() to see if the  
keystroke is actually on the viewport? That might resolve this.

-chuck