[API] Let LuceneTypes.h be used to forward-declare Lucene::*Ptr types

Host programs can now just pull in LuceneTypes.h in their headers without cascading-in nearly as many other headers of Lucene, std:: and boost:: classes.

* Note that some host programs may be using LuceneTypes.h directly, and depend on the (non-forward-) declarations of the classes that this file brings in. These programs should #include "Lucene.h" or some more specific themselves.

Author: rowanj

include/LuceneTypes.h

@@ -7,7 +7,8 @@
 #ifndef LUCENETYPES_H
 #define LUCENETYPES_H
 
-#include "Lucene.h"
+#import <boost/smart_ptr/shared_ptr.hpp>
+#import <boost/smart_ptr/weak_ptr.hpp>
 
 #define DECLARE_SHARED_PTR(Type) \
     class Type; \