Display prices correctly.
Npcs start with cash again.
Npcs cannot get negative cashvalues.
You can force (T) a trade. Any leftover cash increases p->op_of_u.owed
Tweak EATHEALTH

Wasn't the best place for it and there should be positive feedback so
players don't wonder why their health increased.

Since it adds a string, will wait for 0.A.
Signed off on CC BY-SA
Merge fixes to NPC cash handling and EATHEALTH tweak.
Merge signoff.