Patch for /trunk/word2vec.c

```
the hierarchical softmax sampling code missing some situations.
```

Original issue reported on code.google.com by `LMZHs...@gmail.com` on 26 Mar 2015 at 4:23

Attachments:
- [word2vec.c.patch](https://storage.googleapis.com/google-code-attachments/word2vec/issue-29/comment-0/word2vec.c.patch)
