[TRY 3] Add support for tooltips for system tray icons

[James Liggett]

On Wed, 2006-08-30 at 15:37 +0900, Mike McCormack wrote:
> Shouldn't you only initialize comctl32 once, rather than every time 
> there's no icons and we add one?
Sure. I did it like this because Alexandre only wanted to have common
controls initialized when we added an icon so we didn't have to do so
much work at explorer startup. Taking a second look I see how we could
end up initializing common controls more than once. My first thought on
this is to add a boolean variable somewhere that would tell us if we've
already initialized comctl32 so we don't do it more than once. 

James