Use value_true in value_equal and value_less

Use value_true in value_equal and value_less

Both value_equal and value_less use value_as_long to check a
presumably boolean result of calling value_binop.  However,
value_binop in this case actually returns an int as wide as its
arguments, and this approach can then fail for integers wider than
LONGEST.  Instead, rewrite this in a form that works for any size
integer.