message: Add zeros to bitmasks
  Summary:
  Align the strings.
  Code cleanup.
diff: @@ -60,11 +60,11 @@ assert_eq_size!(Option<FrozenPointer<'static, String>>, usize);
  const TAG_BITS: usize = 0b111;
  -const TAG_INT: usize = 0b10;
  +const TAG_INT: usize = 0b010;
  const TAG_STR: usize = 0b100;
  // Pointer to an object, which is not frozen.
  // Note, an object can be changed from unfrozen to frozen, not vice versa.
  -const TAG_UNFROZEN: usize = 0b01;
  +const TAG_UNFROZEN: usize = 0b001;
  unsafe fn untag_pointer<'a, T>(x: usize) -> &'a T {
  cast::usize_to_ptr(x & !TAG_BITS)
  