- Backtracing changed to handle conjunctive tests in instantiations 
  conditions that are a result of unification tests being added for 
  LTIs. It was previously assuming every test was an equality test.
- Fixed crash with rhs deallocation debug printing.  Rhs functions are 
  deallocated before the agent object is deleted, so it was trying to 
  print deallocated rhs function.  Now only prints rhs value if it is 
  a symbol.
- Re-enabled all unit tests.  They now all pass, though some seem to 
  be running very slow (SmemArithmetic and 
  InstantiationDeallocationOverflow).