unknown references in expressions throw an ReferenceNotFoundException
fixed issue #8
debugging
this time it was a real bug in the test code :-[
debuuging seg faults the new tests reveal (and they go real deep into code)
started implementing the EvaluationVisitorTest
added test skeleton for evaluationvisitortest
testrunner updated for fixtures
integrated CppUnit into build system
prepared build system to integrate CppUnit
