Segmentation fault when ast and tables are imported before pandas
```python
import tables
import ast
import pandas
```
This results in a segmentation fault using Anaconda 64 bit under Python 2 and Python 3. 
* Pandas version 0.19.2 as obtained from conda-forge (np112py27_1). 
* Pytables version 3.3.0 as obtained from conda0forge (np112py27_0).
