Add visual cues to Selection/Search button history

[Ldp]

The Selection and Search buttons have a history feature, by clicking the small black downward triangle. There is no visual cue that that part of the button does anything differently than the rest of the button. I suggest adding a vertical separator between the right side history area and the rest of the button, so it's more obvious that there is differing behaviour.

Also, when you first start JOSM, the history is empty, and clicking the history triangle shows nothing. I suggest that there should already be a dropdown then, with a header line saying 'History'. That would make it even more obvious what the dropdown is about.