Foundation build fixes after the merge done by @theod.  Added unit test for the case mentioned in Théo's comments.  This unit test does currently fail because TTObject lacks a copy constructor.
TTElement: implemented = operator for other TTElements -- this is critical because memory from the other TTElement can go away and we need to allocate our own copy of the non-trivial types like TTSymbol.
TTObject: adding the extremely critical copy constructor! Now ref counting increments correctly when making copies.
TTValue: cleanup of ancient and unused 'stringPresent' member.