[dmd-internals] dmd test suite

[Brad Roberts]

I've just checked in the skeleton of a test suite for us to discuss and
hopefully start adding to rather than continuing to expand the non-distributable
one.

I've only tested it on linux, but it should work for any posix system that has
bash, grep, and gnu make installed.  There's a reasonable chance it'd even work
on windows under cygwin, but I haven't tried it.

There's a short documentation blurb at the top of the makefile.  I've only
copied two tests from the existing test suite over as a demonstration of the
usage.  Both are so basic enough that I expect that they're safe to make public.

Parallelism works with standard make arguments, namely -j and -l.

It also includes enough logic to resume interrupted tests by just re-running
make without running 'make clean'.  Additionally, if the dmd binary is updated,
that's sufficient to invalidate and force a re-run of each test.

Current output:

$ make clean
Removing output directory: test_results
$ make -j2
Creating output directory: test_results
Building combinations tool
Running runnable tests
 ... runnable/hello.d  required:  -d    permuted args:
 ... runnable/mars1.d  required:        permuted args: -inline -release -gc -O
-unittest -fPIC

Feedback appreciated.

Later,
Brad