Currently, to_chat is literally just a proc that does user << message.
But it'll let us do output modification in the future, especially for
something like Goon's HTML chat.
Big thanks to PJB for his to_chat script, see
https://github.com/d3athrow/vgstation13/pull/6625 for more details.
- Also adds ABSTRACT and NODROP flags in preparation for removal of
canremove and abstract vars.
- Sorts some of the setup.dm flags so they're in order.
- Replaces 'flags & 2' in policetape.dm with pass_flags & PASSTABLE,
should have the same effect.
