Add LuaJIT 2.0.0.

Though I added a line for LuaJIT in upstream/packages.txt,
cnucnu fails because we cannot get the directory listing of
http://luajit.org/download/ (got http status 403).

```
$ ./cnucnu.py --shell
 None None  URL:> http://luajit.org/download/
 None http://luajit.org/download/  Regex:> DEFAULT
Upstream Versions: Cannot retrieve upstream Version: Upstream Version Retrieval Error: : no upstream version found. - http://luajit.org/download/ - \b[-_](?i)(?:(?:src|source)[-_])?([^-/_\s]*?\d[^-/_\s]*?)(?:[-_.](?:src|source|orig))?\.(?:tar|t[bglx]z|tbz2|zip)\b
 \b[-_](?i)(?:(?:src|source)[-_])?([^-/_\s]*?\d[^-/_\s]*?)(?:[-_.](?:src|source|orig))?\.(?:tar|t[bglx]z|tbz2|zip)\b http://luajit.org/download/
```