Increase clickable area for the tab overflow button

The button frame has been extended to the top/bottom of the tab bar and on Yosemite there are 3 pixels of padding to the right of the image (which are thus part of the button and hence clickable).
OakChooser subclasses can disable reload on filter string changes

For example if the user adds a line number suffix, we do not want to trigger re-filtering of items (which resets the selection).
Support line number suffix in file chooser when filtering by glob

Also prevent re-filtering items (and thus losing selection) if the effective (normalized) filter string is unchanged.