Get mutlifile compilation working again and add a test for it

unittests/multifile_test_chai.cpp

@@ -0,0 +1,12 @@
+#include "multifile_test_chai.hpp"
+
+Multi_Test_Chai::Multi_Test_Chai()
+  : m_chai(new chaiscript::ChaiScript())
+{
+}
+
+
+boost::shared_ptr<chaiscript::ChaiScript> Multi_Test_Chai::get_chai()
+{
+  return m_chai;
+}