* the saveable tables were initialized too late when reading in the actors.
* the abort messages for the saveables did not show. We need to use I_FatalError here, plus some actor list modifications to make this work.
Unfortunately this had to be done in the base class so that we can still maintain the walls in a global array.
The tradeoffs of better abstractions would be far too costly here than the added 16 bytes to the wall struct.
Also optimized the base64 encoder to avoid creating endless memory copies, thanks to using std::string which is a really poor container for this kind of stuff when workig with larger blocks of data.
