Re:GtkComboBoxEntry buttons are wider

[Bill Haneman <Bill Haneman Sun COM>]

Hi:

The GtkComboBoxEntry arrows really ought to have a themeable size 
(either keyed to font size, or with their own size property).

If we make the ComboBox arrows smaller, then we certainly need to make 
sure they're themeable so that they stay easily visible in the 
'LargePrint' themes.   So if anybody starts poking around the rendering 
code for the arrows, this would be an excellent additional small bit to 
add to the patch.

regards,

- Bill