style: [patch 3/22] reduce include dependencies in some headers

Used cppclean to help identify useless includes and removed them. This
involved erroneously included headers, but also cases where forward
declarations could have been used rather than a full include.

src/sim/sim_object.hh

@@ -49,21 +49,18 @@
 #ifndef __SIM_OBJECT_HH__
 #define __SIM_OBJECT_HH__
 
-#include <iostream>
-#include <list>
-#include <map>
 #include <string>
 #include <vector>
 
-#include "enums/MemoryMode.hh"
 #include "params/SimObject.hh"
 #include "sim/drain.hh"
+#include "sim/eventq.hh"
 #include "sim/eventq_impl.hh"
 #include "sim/serialize.hh"
 
-class BaseCPU;
-class Event;
+class EventManager;
 class ProbeManager;
+
 /**
  * Abstract superclass for simulation objects.  Represents things that
  * correspond to physical components and can be specified via the