Strict aliasing rules broken

When building libcork on CentOS with gcc 4.4.6, the compiler generates an error on file `core/hash.h`:

```
error: dereferencing pointer ‘curr’ does break strict-aliasing rules
```

This error occurs at line 91, but the culprit appears to be [line 79](https://github.com/redjack/libcork/blob/develop/include/libcork/core/hash.h#L79):

```
const uint32_t  *blocks = (const uint32_t *) src;
```