placeholder for the ready queue, needed by environment, and factorized
stubs for tests in a separate directory. Updated makefile including environment, concrete_environment, ready_queue, but NOT the stubs and/or the tests.
git-svn-id: svn://svn.gna.org/svn/sgpemv2/trunk@685 3ecf2c5c-341e-0410-92b4-d18e462d057c