New Button Relief Attributes

Buttons, checkbuttons, and radiobuttons all gained an -overrelief option, which specifies a relief style to use when the mouse cursor is over the widget. Checkbutton and radiobutton widgets also gained an -offrelief option, which specifies the relief style to use for the widget when the widget is in an "off" state and the indicator is not drawn. These new relief options make it much easier to create "toolbars" from a collection of button widgets. (TIP #82)