message: fix test on i686
diff: #![feature(core_intrinsics)]
  +use std::mem;
  +
  fn main() {
  let x: Option<Box<[u8]>> = unsafe {
  let z = std::intrinsics::add_with_overflow(0usize, 0usize);
  std::mem::transmute::<(usize, bool), Option<Box<[u8]>>>(z)
  };
  let y = &x;
  - // Now read this bytewise. There should be 9 def bytes followed by 7 undef bytes (the padding after the bool) in there.
  + // Now read this bytewise. There should be (ptr_size+1) def bytes followed by (ptr_size-1) undef bytes (the padding after the bool) in there.
  let z : *const u8 = y as *const _ as *const _;
  - for i in 0..9 {
  + let first_undef = mem::size_of::<usize>() as isize + 1;
  + for i in 0..first_undef {
  let byte = unsafe { *z.offset(i) };
  assert_eq!(byte, 0);
  }
  - let v = unsafe { *z.offset(9) };
  + let v = unsafe { *z.offset(first_undef) };
  if v == 0 {} //~ ERROR attempted to read undefined bytes
  }
  