Incorrectly used free() in _psutil_osx.c

_From [alexey.p...@qik.com](https://code.google.com/u/105030590945765989247/) on December 23, 2011 16:18:40_

```
free(fds_pointer);
...
fdp_pointer = &fds_pointer[i];

fds_pointer is freed, then accessed.
```

_Original issue: http://code.google.com/p/psutil/issues/detail?id=240_
