This is needed as a workaround to support Waves VST3 plugins.
Right now does does not actually fix the issue because the arguments are
not updated in the subclasses. The next commit will fix this.
Apparently this can actually make a difference in some cases, and the
C++ Core Guideliens recommend doing this on all default constructors,
destructors, and all functions that can not throw (and thus also don't
allocate).
This is quite a huge refactor, but note everything is consistent (and
we're going to need one or two more of these `Vst3*Proxy` objects).
Right now nothing extends `IHostApplication`, but this way it will be
trivial to add support for more host context interfaces.
Robbert van der Helm