The correct condition for adding the extra border to the buttons that
would be clipped without it due to the bezel style used for them is to
check that their height is < 20, as SetBezelStyleFromBorderFlags(),
which determines the bezel to use, does, and not if their width is 16,
as this is not the same thing, especially for non-square buttons.
Closes https://github.com/wxWidgets/wxWidgets/pull/1887
0941b25a97