message: privatize fields in attrs classes
diff: namespace IR {
  class ParamAttrs final {
  + unsigned bits;
  +
  public:
  enum Attribute { None = 0, NonNull = 1<<0, ByVal = 1<<1, NoCapture = 1<<2,
  ReadOnly = 1<<3, ReadNone = 1<<4 };
  - unsigned bits;
  -
  ParamAttrs(unsigned bits = None) : bits(bits) {}
  bool has(Attribute a) const { return (bits & a) != 0; }
  @@ -24,12 +24,12 @@ public:
  class FnAttrs final {
  + unsigned bits;
  +
  public:
  enum Attribute { None = 0, NoRead = 1 << 0, NoWrite = 1 << 1,
  ArgMemOnly = 1 << 2, NNaN = 1 << 3, NoReturn = 1 << 4 };
  - unsigned bits;
  -
  FnAttrs(unsigned bits = None) : bits(bits) {}
  bool has(Attribute a) const { return (bits & a) != 0; }
  