Implement the RDMD test-suite

http://d.puremagic.com/issues/show_bug.cgi?id=9662

Initial attempt was [here](https://github.com/D-Programming-Language/dmd/pull/2235).

The test suite needs to be run from the `tools` directory, using the command:

```
$ dmd -unittest -run rdmd.d
```

The test-suite was only tested on Windows. Also, the tests will only work with a DMD git-head version. The stdout/stderr printing apparently changed since 2.063.2, as the `output` checks fail with the older version of the compiler (that's the only reason I can think why they fail).