Also changed all "if (this==NULL) return;"s.
Fixes some -Wtautological-undefined-compare warnings.
Quoting Clang:
"'this' pointer cannot be null in well-defined C++ code; comparison may
be assumed to always evaluate to false"
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. :)
