v0.13.0

Added

• call_nth/2 and countall/2, the last two predicates of the Prolog prologue.
  call_nth(Goal, Nth) counts the solutions of Goal and, with Nth bound, stops at that
  solution without leaving a choice point; call_nth(Goal, 0) fails without calling Goal.
  countall(Goal, N) counts every solution without collecting them. Both raise
  type_error(integer, N) and domain_error(not_less_than_zero, N) for a bad count, and
  countall/2 the instantiation and callable errors for its goal first.
• maplist/6..8, nth0/4, and nth1/4, which the prologue also lists; the /4 forms give the
  list without the element.

Fixed

• succ/2 raises domain_error(not_less_than_zero, N) for a negative argument, rather than
  type_error(not_less_than_zero, N), and checks both arguments in the prologue's order, so
  succ(1, 1+1) is type_error(integer, 1+1).
• nth0/3 and nth1/3 raise type_error(integer, I) for an index that is not an integer, which
  used to enumerate the list without end on a partial one, and domain_error(not_less_than_zero, I)
  for a negative index, which used to fail.