[crossfire] Diseases question

[Nicolas Weeger]

Hello.

I fixed a bug concerning diseases that had a negative "value", but got a
question concerning maxhp: according to the doc, negative means
"permanent outside the host". And positive "max ticks the disease
stays". So the obvious question is: what about 0? Should the disease
stay permanent? Disappear right away?
Asking because my fix in server/disease.c:173 may be wrong depending on
the reply :)

Ryo