SCI32: split up SCI2.1 into EARLY/MIDDLE/LATE

- Detection works via signatures (couldn't find a better way)
- new kString subcalls were introduced SCI2.1 LATE
- kString now has signatures and is split via subcall table
- kString fix, so that KQ7 doesn't crash, when starting a chapter
- Sci2StringFunctionType removed, because no longer needed

engines/sci/resource.h

@@ -559,6 +559,8 @@ protected:
 	ViewType detectViewType();
 	bool hasSci0Voc999();
 	bool hasSci1Voc900();
+	bool checkResourceDataForSignature(Resource *resource, const byte *signature);
+	bool checkResourceForSignatures(ResourceType resourceType, uint16 resourceNr, const byte *signature1, const byte *signature2);
 	void detectSciVersion();
 };