message: Fix undefined behavior in rng.h
diff: @@ -140,8 +140,8 @@ namespace ml {
  ulong MWC()
  { return (((znew() << 16) + wnew()) & 0xfffffffful); }
  ulong SHR3()
  - { jsr ^= (jsr << 17); jsr ^= (jsr >> 13);
  - return (jsr = ((jsr ^= (jsr << 5)) & 0xfffffffful)); }
  + { jsr ^= (jsr << 17); jsr ^= (jsr >> 13); jsr ^= (jsr << 5);
  + return (jsr = jsr & 0xfffffffful); }
  ulong CONG()
  { return (jcong = ((69069 * jcong + 1234567) & 0xfffffffful)); }
  ulong rand_int32() // [0,2^32-1]
  