Damage caused by Succumb verb changed

- Instead of causing a flat 200 Oxygen Loss, Succumb will now cause
enough damage to kill the target + 15 for safety
- Really only a small tweak to make Succumb less annoying. Now a person
who succumbed will have about the same damage that a person that would
normally have died out would
Merge pull request #1124 from dylanstrategie/Succumb-Verb

Damage caused by Succumb verb changed