Core/Objects: added ToUnit(), ToGameObject() (will be used in future)

Core/Unit:
- added SetFacing() function, using proper packet implementetion (spline type)
- added GetAuraCount() function (will be used in future)
Core/Creature: renamed one unknown type_flag

--HG--
branch : trunk

src/server/game/AI/ScriptedAI/ScriptedFollowerAI.cpp

@@ -54,7 +54,7 @@ bool FollowerAI::AssistPlayerInCombat(Unit* pWho)
         return false;
 
     //experimental (unknown) flag not present
-    if (!(me->GetCreatureInfo()->type_flags & CREATURE_TYPEFLAGS_UNK13))
+    if (!(me->GetCreatureInfo()->type_flags & CREATURE_TYPEFLAGS_AID_PLAYERS))
         return false;
 
     //not a player