RadioButto -- Overview
------------------------------------------------------------------------------
 Class Function

 RadioButto()    Create a new RadioButto object
------------------------------------------------------------------------------
 Exported Instance Variables

 bitmaps         An array of bitmap files to be displayed
 buffer          Logical value indicating whether a radio button is selected
 caption         Character string describing the radio button on the screen
 capCol          Indicates column where radio button's caption is displayed
 capRow          Indicates column where radio button's caption is displayed
 cargo           User-definable variable
 col             Indicates the column where the radio button is displayed
 colorSpec       Indicates colors used by the radio button's display() method
 fBlock          Code block evaluated at each input focus change
 hasFocus        Logical value indicating the input focus
 row             Indicates the row where the radio button is displayed
 sBlock          Code block evaluated at every state change
 style           Indicates characters used by radio button's display() method
------------------------------------------------------------------------------
 Exported Methods

 display()       Shows a radio button and its caption on the screen
 hitTest()       Indicates position of mouse cursor relative to radio button
 isAccel()       Determines if a key press is interpreted as a user request
 killFocus()     Takes input focus away from the RadioButto object
 select()        Changes the state of a radio button
 setFocus()      Gives input focus to the RadioButto object