Whenever creating a functor to be launched in the execution environment
using the device adapter Schedule algorithm, you had to also create a
couple of methods to handle error message buffers. For convenience, lots
of code started to just inherit from WorkletBase. Although this worked,
it was a misnomer (and might cause problems in the future if worklets
later require different things from its base). To get around this
problem, add a FunctorBase class that is intended to be used as the
superclass to functors called with Schedule.
