Proxy class that supports the asynchronous function implementation of older XLL+ versions.
The CRtdLink class was used by XLL+ version 6 and below. An instance of the class was inserted into the project's application class. As of XLL+ version 7, the CRtdAsyncManager is used instead. An instance of this class is created, on demand, inside the application class base class, CXllApp.
This deprecated class merely acts as a proxy for the instance of CRtdAsyncManager contained by the base class.