Reverting dtor devirtualization patch.

_sabre_: it has a major problem: by the time ~Value is run, all of the "parts" of the derived classes have been destroyed
_sabre_: the vtable lives to fight another day

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@44760 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Value.h

@@ -66,11 +66,8 @@ private:
   friend class SymbolTable;      // Allow SymbolTable to directly poke Name.
   ValueName *Name;
 
-private:
   void operator=(const Value &);     // Do not implement
   Value(const Value &);              // Do not implement
-protected:
-  static void destroyThis(Value*);
 
 public:
   Value(const Type *Ty, unsigned scid);