- added a StartSlideshow ACS and ZScript command and extended the functionality to specify the slideshow's name when starting it.
This is for triggering any kind of intermission definition in the middle of a level - keep in mind that this may not be set up to loop!
- Changed the glass shards so that they do not have to override FloorBounceMissile. It was the only place where this was virtually overridden and provided little usefulness.
- made 'out' variables work.
- fixed virtual call handling for HandlePickup.