bug#43764: Calc shift right broken

[Mattias Engdegård]

> What about a narrower change: clip the value after shifting right instead of 
> before?

On the other hand it would introduce an inconsistency with arithmetic right 
shift which ignores bits above the word size.
Thus I will do nothing at all unless Vincent or anyone else speaks up.

However, this bug has already been a success since inspecting the code revealed 
a bug in the arithmetic right shift that has now been fixed, and there is now a 
fairly comprehensive test for all binary shift and rotate operations which 
should make future changes a lot safer and easier.