small refactoring
fixing weird messages on decayed food for strangevores

"Blecch! Rotten metal! The world spins and goes dark." - now it will be "Blecch! Contaminated metal! The world spins and goes dark."

thanks to all people that participated in http://www.reddit.com/r/nethack/comments/1afd5t/fixing_blecch_rotten_metal_the_world_spins_and/ thread

Fixes #4 ("Blecch! Rotten metal! The world spins and goes dark.")