A base class for things which need to inherit from both TypedWritable and from ReferenceCount.
It's convenient to define this intermediate base class instead of multiply inheriting from the two classes each time they are needed, so that we can sensibly pass around pointers to things which are both TypedWritables and ReferenceCounters.
See also TypedObject for detailed instructions.
Definition at line 35 of file typedWritableReferenceCount.h.