[qvtd-dev] Slow down

[Ed Willink <ed@xxxxxxxxxxxxx>]

Hi Horacio

I've been trying to introduce some discipline to the lash up I used to 
get performance figures and find that the QVTi Interpreter has got 25% 
slower. The problem is that your retiming of the creation of the nested 
evaluation visitor means that additions to the environment regularly 
throw an IAE causing the retry as a replacement. Normal execution should 
not throw exceptions.

In principle the retiming may be fractionally faster since there is one 
fewer parameters to pass, but the IAEs need to be fixed.

    Regards

        Ed