Hrm is a really nasty ommission. The lack of this destructor was causing abstract

types to never be deleted, manifesting itself as many OpaqueType objects being
leaked.  Whoops.

llvm-svn: 10601

llvm/include/llvm/AbstractTypeUser.h

@@ -143,6 +143,8 @@ public:
     addRef();
   }
 
+  ~PATypeHolder() { dropRef(); }
+
   operator const Type *() const { return get(); }
   const Type *get() const;