#20 dspsr: dspExtension rethink

[Willem van Straten]

Currently, an array of Reference:To<dspExtension> class instances is cloned at the start of every out-of-place Operation. Behind the scenes, Reference::Able inherits HeapTracked, which searches for the base address of the instance in a std::list ... this might be expensive, and it would be better to minimize the number of new/delete operations after everything is set into motion.

[Willem van Straten]

The dspExtension class has been removed from the library. Although it was never tested if this change improved performance, it greatly simplified the multi-threaded code.