msgpack-rpc tests fail mpio compiled with clang

I compiled jubatus-mpio with clang 3.0, compiled jubatus-msgpack-rpc with gcc 4.7.2 then rpc tests fail. and test/Makefile.am option missed `-msgpack` instead of `-lmsgpack`.

```
$ make check
(snip)
2013-01-23 11:58:40 transport/tcp.cc:247: connecting to 127.0.0.1:18811
```

I wrote test environment.
https://github.com/jubatus/jubatus/issues/120#issuecomment-12406482
