Message 305205 - Python tracker

Hi,

The following program crashes for me using the current Python3.7 master:

```
import plistlib
plistlib.loads(b'\xdd\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
               b'\xda\x0cw\xb7\x00\x00\x00\x00\x00\x00\x00\xc7\x00'
               b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\xd6\xd5\x00'
               b'\x00\x00\x00\x00\x00\x00\x04\x00\x00\x00\x00\x00'
               b'\x00\x00\x00\x00\x10\x00\x00\x00\x00\x00\x00',
               fmt=plistlib.FMT_BINARY)
```

The last few lines look like
```
  File "/usr/lib/python3.5/plistlib.py", line 728, in _read_object
    ] = self._read_object(self._object_offsets[o])
  File "/usr/lib/python3.5/plistlib.py", line 728, in _read_object
    ] = self._read_object(self._object_offsets[o])
  File "/usr/lib/python3.5/plistlib.py", line 723, in _read_object
    key_refs = self._read_refs(s)
  File "/usr/lib/python3.5/plistlib.py", line 647, in _read_refs
    return self._read_ints(n, self._ref_size)
  File "/usr/lib/python3.5/plistlib.py", line 644, in _read_ints
    for i in range(0, size * n, size))
RecursionError: maximum recursion depth exceeded in comparison
```

This bug was found using an alpha version of python-fuzz.