Core: Fix non-PCH building

src/server/scripts/Northrend/Naxxramas/boss_thaddius.cpp

@@ -15,6 +15,10 @@
  * with this program. If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include "ScriptMgr.h"
+#include "ScriptedCreature.h"
+#include "SpellScript.h"
+
 #include "naxxramas.h"
 
 //Stalagg