Fix various brokenness with exploding monster attributions (Midn8)

The most obvious breakage is that the player was incorrectly getting
penance for blazeheart core explosions, but the player also was not getting
XP for some things like ballisto spore explosions. I *think* this should
straighten most of that out.

crawl-ref/source/mon-explode.cc

@@ -43,16 +43,17 @@ static void _setup_base_explosion(bolt & beam, const monster& origin)
     beam.target       = origin.pos();
     beam.explode_noise_msg = "You hear an explosion!";
 
-    if (!crawl_state.game_is_arena()
-        && origin.friendly() && origin.was_created_by(you))
+    if (!crawl_state.game_is_arena() && origin.friendly())
     {
-        if (origin.is_abjurable())
+        // Prisms, ball lightning, etc. are considered to have been damage
+        // caused by the player directly.
+        if (!origin.is_abjurable() && origin.was_created_by(you))
+            beam.thrower = KILL_YOU;
+        else
         {
             beam.thrower = KILL_MON;
-            beam.source_id = ANON_FRIENDLY_MONSTER;
+            beam.source_id = MID_ANON_FRIEND;
         }
-        else
-            beam.thrower = KILL_YOU;
     }
     else
         beam.thrower = KILL_MON;
@@ -103,7 +104,7 @@ static void _setup_blazeheart_core_explosion(bolt & beam, const monster& origin)
     // Don't place the player under penance for their golem exploding,
     // but DO give them xp for its kills.
     beam.thrower      = KILL_MON;
-    beam.source_id    = MID_PLAYER;
+    beam.source_id    = MID_ANON_FRIEND;
 
     // This is so it places flame clouds under the explosion
     beam.origin_spell = SPELL_FORGE_BLAZEHEART_GOLEM;