panel item prefs window resizing

[Jasper Huijsmans]

...
> 
> hmmmm... font size is 13pt, so i doubt that's it.  my res is 1600x1200, 
> perhaps that could have something to do with it.  or the missing icon.  
> is it supposed to have an icon?  i wonder why it's missing...  i'll 
> figure it out later =p.
> 

It's not suposed to have an icon. Yet. I have implemented a way for 
plugins to set an icon, but nothing is using it yet.

The header looks better if there is some space around the label, so I 
set it to 32px. I'll think about a better way (possibly involving border 
width or padding ;-)