TV_field->buttonize (ul_oocbs)

	TV_field.s.r = buttonize(this_function.s.r, window.s.r, row.i4.v,
				 column.i4.v, label.i1a.r, color.i4.v)

	Create a button for the function.  This should probably be in
	TV_matrix, but it isn't.  So it's in Class Function instead.
	Later on it will be moved to button state (create a button given a
	function, or install a new function).