syntax: "super" is a synonym of "special"

syntax: "super" is a synonym of "special"

Nit syntax is declarative with nouns.

Examples:
  "class X" -> X is a class
  "fun x" -> x is a function of the class
  "var _x" -> _x is an instance variable of the class
  "init x" -> x is a constructor of the class

Therefore, it can make sense that the declaration
of superclasses use the same scheme.

  "super Y" -> Y is a superclass of the class
instead of the current
  "special Y" -> the class specializes Y
                (or the class is a special kind of Y)

Signed-off-by: Jean Privat <jean@pryen.org>