Modifier to make a `func` on a type a free function

[anon9791410]

@sveinhal

I think we should keep the static func but extend symbol lookup rules to accept the “naked” function name when calling a static function from a non-static context.

For sure, because reaching out beyond Self to enclosing types already works that way.

enum ReallyOutThere {
  static func outerStaticMethod() { }
  static func reallyOutThereMethod() { }

  enum Outer {
    static func outerStaticMethod() { }

    struct Inner {
      static func innerStaticMethod() { }

      func instanceMethod() {
        innerStaticMethod() // does not compile; requires `Self.`
        outerStaticMethod() // compiles! Calls `Outer.outerStaticMethod`.
        reallyOutThereMethod() // compiles!
      }
    }
  }
}