This module defines a "button" object for use with the TV window
interface. A TV_number (a "changeable" TV_button) inherits all of
the functionality of the TV_button class, with the additional
functionality of being able to change its appearance (text, or label)
by reading from the "TV" screen.
V00.00 James Holt April 21, 1991
Original - cloned from tv_field.h.
V00.01 Andrew Braun February 29, 1996
Corrected create_tv_number description to match prototype.
v00.02 Andrew Braun October 7, 1996
Corrected creat_tv_number window_id description to match