SCUMM: changed handling of _activeInventory/_activeActor to _activeObject(2)/_activeObject(2)Type

Note: the transition is not completed yet. The code compiles but is probably not runnable as not every occurrence of _activeInventory has been properly replaced.
The usage of _v0ObjectIndex and _v0ObjectInInventory should be revised too and both variables should be replaced by another mechanism (maybe by using a single variable "obj = (type << 8) | id").

- moved v0 only vars _activeInventory, _activeObject, _activeVerb from  ScummEngine_v2 to ScummEngine_v0
- removed _activeActor, _activeInvExecute, _activeObject2Inv and _activeInventory. They are handled by _activeObject/_activeObjectType and _activeObject2/_activeObject2Type now.
- removed _activeObject(2)Index as they only bloat the code without any benefit (?)
- merge prep-name tables from ScummEngine_v2::drawPreposition() and ScummEngine_v0::drawSentenceWord() by introducing ScummEngine_v2::drawPreposition()
- rename ObjectData.flags -> obj_type (quick-fix only, needs review! Maybe obj_nr and obj_type can be merged into one var: obj_nr = (obj_type << 8) | obj_nr)
- o_unknown2 is negation of o_ifActiveObject (o_ifNotEqualActiveObject2)
- renamed o_ifActiveObject -> o_ifEqualActiveObject2 as it acts only on _activeObject2
- renamed ScummEngine_v0::drawSentenceWord() -> ScummEngine_v0::getObjectName()

engines/scumm/saveload.cpp

@@ -822,7 +822,7 @@ void ScummEngine::saveOrLoad(Serializer *s) {
 		MKLINE(ObjectData, parent, sleByte, VER(8)),
 		MKLINE(ObjectData, state, sleByte, VER(8)),
 		MKLINE(ObjectData, fl_object_index, sleByte, VER(8)),
-		MKLINE(ObjectData, flags, sleByte, VER(46)),
+		MKLINE(ObjectData, extra, sleByte, VER(46)),
 		MKEND()
 	};