Support compiling files that are in the attic

Since these files are not actively maintained, we don't assume that
the project actually has any, nor are they part of the default build.
Move old files into the attic

The attic are the place where files which we don't use right now, but
which we acknowledge some amount of valuable time has been spent on and
which may be usable some day in the future, so we don't have the
conscience to right out delete them.

These files are not expected to compile, and certainly not to run and
produce sensible results, anymore. However, with some work they can
possibly be converted into proper unit tests or examples.
Issue warning about the status of files in the attic
Merge pull request #302 from rolk/302_attic

Put old "non-unit-tests" in the attic instead