focustbutton: will draw a tbutton on the
screen using the focus colors and wait for input. The button is
selected by pressing the spacebar or enter key. The tab key is used to
move off the button without selecting it. If the user presses the enter
key or spacebar, focustbutton: returns 1 in Rx. If the tab key is
pressed, 0 is returned in Rx.
value of the tbutton widget: 1 if selected, 0 if not selected.
name: The name of the tbutton.