If ENABLE_STAT_TRACKING is disabled, SQL completely fails

Created by: JamieH

https://github.com/d3athrow/vgstation13/blob/Bleeding-Edge/code/libs/db/core.dm#L27

I've just spent the last couple of hours into trying to work out why I couldn't get MySQL working...

Track population and death statistics

Comment this out to disable

ENABLE_STAT_TRACKING

This really should be better documented or fixed