MaxHP, MaxSP and Autotrade fixes
- Percentual bonuses to MaxHP and MaxSP will now always be rounded down (Aegis style)
- Added a security check when calculating MaxHP and MaxSP so there can't be a number underflow (bugreport:9369)
- When an auto-vendor gets logged out because of at_timeout, his store will be deleted and no longer restored after server restart (bugreport:9370)