Issue 9662 - Introduce test-suite for RDMD.

http://d.puremagic.com/issues/show_bug.cgi?id=9662

I have a few problems though:

The makefile won't re-run the tests when RDMD is re-built, only when DMD is re-built.

Another problem:

RDMD is currently hardcoded to a tools repo in the makefile (e.g. on Windows: `export RDMD=../../tools/rdmd.exe`). This shouldn't be a problem since the user can override this when calling the makefile, but maybe the autotester machines will have to be updated to take this into account.

The switches which I didn't test are:

- `--chatty` - not sure how to properly test this
- `--force` - i'd need a test where not using --force would fail
- `--makedepend` - this is too platform specific, we'd probably need a good shell script to test this instead of using `TEST_OUTPUT`
- `--man` - not sure how to test this, it spawns a browser
- `--shebang` - I have no idea what this flag does

Hacking at the actual test-runner and the makefile is a drag, if someone else wants to take over and implement this properly so RDMD tests are re-run when RDMD is re-built, it would be great.

I hope this is just a good start towards an RDMD test-suite.