Change strategy for handling true and false to avoid some initialization order problems and improve performance. Add support for negative integer literals. Update samples to reflect true/false change.

#{
fib <- :n {
  if: n < 2 {
    1
  } else: {
    (fib: n-1) + (fib: n-2)
  }
}

main <- {
  print: (string: (fib: 30)) . "\n"
}

}