In arena mode always announce when a monster submerges or surfaces, make

submerged monsters visible to the player except for them still showing as a disturbance in the water, and prefix the name of submerged monsters with "submerged".

Fix simple_monster_message() to always give the message during arena mode.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8167 c06c8d41-db1a-0410-9941-cceddc491573

Created by  zelgadis  on January 3, 2009
H6VLPIMXKMZVGZVQFUUSW73LRHC3KTIFE3JNSCZ7PJALXP62RIGAC
Change contents