Conflict based off of charisma

Higher charisma will make it more likely for monsters to be affected.
Conflict will also now require the monster to see the hero.

Originally from SporkHack by Derek Ray.

src/mhitm.c

@@ -116,7 +116,7 @@ fightm(register struct monst *mtmp)
     nmon = 0;
 #endif
     /* perhaps the monster will resist Conflict */
-    if (resist(mtmp, RING_CLASS, 0, 0))
+    if (resist_conflict(mtmp))
         return 0;
 
     if (u.ustuck == mtmp) {