-Lot of runtime fixes for advance diseases.

-Added two new symptoms, fever and itching.
-Changed some stats on existing symptoms.
-Emotes sucks so I used visible_message if there was no preset emote.

git-svn-id: http://tgstation13.googlecode.com/svn/trunk@5021 316c924e-a436-60f5-8080-3fe189b3f50e

code/__HELPERS/lists.dm

@@ -304,4 +304,9 @@ proc/listclearnulls(list/list)
 			if(bitfield & bit)
 				r += bit
 
-	return r
+	return r
+
+/proc/safe_pick_list(var/list/L)
+	if(L.len)
+		return pick(L)
+	return null