some J3D/misc cleanup (#2628)

* some j3d cleanup

* begin using uintptr_t

* j3dgraphbase cleanup

* j3dgraphanimator cleanup

src/d/actor/d_a_e_dn.cpp

@@ -3289,7 +3289,7 @@ static int useHeapInit(fopAc_ac_c* a_this) {
     }
 
     J3DModel* model = i_this->mpModelMorf->getModel();
-    model->setUserArea((u32)i_this);
+    model->setUserArea((uintptr_t)i_this);
 
     for (u16 i = 0; i < model->getModelData()->getJointNum(); i++) {
         if (i != 0) {