CGameHandler::applyBattleEffects: improve Fire Shield support

Now damage is limited to total health of defending stack and clone have no file shield damage. In same time damage calculation is likely remain incorrect.

lib/BattleState.cpp

@@ -988,6 +988,11 @@ const CGHeroInstance * CStack::getMyHero() const
 	return nullptr;
 }
 
+ui32 CStack::totalHelth() const
+{
+	return (MaxHealth() * (count-1)) + firstHPleft;
+}
+
 std::string CStack::nodeName() const
 {
 	std::ostringstream oss;