Always disable scroll and allow move on editable combobox
Following #5322 (closed), the scroll behavior of ComboBox (from GTK) is astonishing for most of the users. This is mainly because ComboBox is used for some fields (Selection, Char, Reference etc.) on form view which are inside a scrolling window. So user expect to scroll the window but if he is by chance on a ComboBox, he will change the value of it instead of scrolling.
I think it is less astonishing (and less annoying) to prevent the modification with scroll.
Also all ComboBox shoud be prevented to move if they are not editable.