add support for declared cursors

Declare a cursor with the Finder::declare_cursor() method and next get the cursor with get_cursor():
morm::Cursor<MyObject> cursor = finder.
  declare_cursor("mycursorname").
  select().
  raw("ORDER BY column_name ASC").
  get_cursor();

The cursor now can be used with fetch.*() methods and then get() or get_list():
MyObject myobject = cursor.fetch_next().get();
std::list<MyObject> myobjects = cursor.fetch_forward_count(10).get_list();

src/dbconnector.cpp

@@ -5,7 +5,7 @@
  */
 
 /*
- * Copyright (c) 2018-2022, Tomasz Sowa
+ * Copyright (c) 2018-2023, Tomasz Sowa
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -144,6 +144,11 @@ bool DbConnector::query_remove(const char * query_str, QueryResult & query_resul
 	return query(query_str, query_result);
 }
 
+bool DbConnector::query_declare_cursor(const char * query_str, QueryResult & query_result)
+{
+	return query(query_str, query_result);
+}
+
 
 
 bool DbConnector::query_select(const pt::TextStream & stream, QueryResult & query_result)
@@ -166,6 +171,12 @@ bool DbConnector::query_remove(const pt::TextStream & stream, QueryResult & quer
 	return query(stream, query_result);
 }
 
+bool DbConnector::query_declare_cursor(const pt::TextStream & stream, QueryResult & query_result)
+{
+	return query(stream, query_result);
+}
+
+
 
 bool DbConnector::begin()
 {
@@ -910,4 +921,6 @@ const char * DbConnector::query_last_sequence(const wchar_t * sequence_table_nam
 	return nullptr;
 }
 
+
+
 }