Method evaluate

\brief Determine if two boolean Varnodes hold related values The values may be the \e same, or opposite of each other (\e complementary). Otherwise the values are \e uncorrelated. The trees constructing each Varnode are examined up to a maximum \b depth. If this is exceeded \e uncorrelated is returned. \param vn1 is the first boolean Varnode \param vn2 is the second boolean Varnode \param depth