The code used to store the world pointer as a console variable
"pwoCurrentWorld" of type INDEX (int32) - that won't work for 64bit, so
I added CShell::SetCurrentWorld() and CShell::GetCurrentWorld() and
store it as a pointer.
This was a _ton_ of changes, made 15 years ago, so there are probably some
problems to work out still.
Among others: Engine/Base/Stream.* was mostly abandoned and will need to be
re-ported.
Still, this is a pretty good start, and probably holds a world record for
lines of changes or something. :)