Special functions (pure, bind): namespaced

[Janiczek]

Instead of

module Logger {
  pure(a: a): Logger[a] = ...
}

we should make these special syntax (not names usually available to users), without making them reserved words.

Eg.

module Logger {
  Cara.pure(a: a): Logger[a] = ...
}

or

module Logger {
  `pure`(a: a): Logger[a] = ...
}