Register update

I just committed a change to the code that moves the registers into 
the interpreter structure rather than accessing the things indirectly 
as we were before. Pushes and pops are a little slower as there are 
memcpys involved now, but register access itself should be faster as 
there's one fewer level of indirection.

Yes, four of the stacks.t tests fail. We need to patch that one 
up--I'll be taking a shot in the morning when things have had a 
chance to settle a bit, but I wanted to get this bit in to start.
-- 
                                         Dan

--------------------------------------"it's like this"-------------------
Dan Sugalski                          even samurai
dan@sidhe.org                         have teddy bears and even
                                       teddy bears get drunk

• Register update by Dan Sugalski