Trying to print Series/DataFrame with column of void dtype throws exception
Trying to print anything containing a V\* (void) type throws in `isnull`:

``` python
>>> import numpy as np
>>> import pandas as pd
>>> arr = np.array([b'foo'], dtype='V')
>>> arr
array([[102 111 111]],
      dtype='|V3')
>>> s = pd.Series(arr)
>>> s[0]
[102 111 111]
>>> s
TypeError: ufunc 'isnan' not supported for the input types, and the inputs could 
not be safely coerced to any supported types according to the casting rule ''safe''
```

From the looks of it, `pandas.core.common._isnull_ndarraylike` (and maybe some other methods?) should take care of this, e.g. return an array filled with False.

Here's the relevant part of the traceback:

```
pandas/formats/format.py in _format_strings(self)
   2057             vals = vals._values
   2058
-> 2059         is_float = lib.map_infer(vals, com.is_float) & notnull(vals)
   2060         leading_space = is_float.any()
   2061

pandas/core/common.py in notnull(obj)
    248     pandas.isnull : boolean inverse of pandas.notnull
    249     """
--> 250     res = isnull(obj)
    251     if lib.isscalar(res):
    252         return not res

pandas/core/common.py in isnull(obj)
     89     pandas.notnull: boolean inverse of pandas.isnull
     90     """
---> 91     return _isnull(obj)
     92
     93

pandas/core/common.py in _isnull_new(obj)
     99         raise NotImplementedError("isnull is not defined for MultiIndex")
    100     elif isinstance(obj, (gt.ABCSeries, np.ndarray, pd.Index)):
--> 101         return _isnull_ndarraylike(obj)
    102     elif isinstance(obj, gt.ABCGeneric):
    103         return obj._constructor(obj._data.isnull(func=isnull))

pandas/core/common.py in _isnull_ndarraylike(obj)
    190         result = values.view('i8') == tslib.iNaT
    191     else:
--> 192         result = np.isnan(values)
    193
    194     # box

TypeError: ufunc 'isnan' not supported for the input types, and the inputs could 
not be safely coerced to any supported types according to the casting rule ''safe''
```
