The function mongo_cursor_get_more() should not call mongo_cursor_destroy(),
because then it's impossible to know whether this should be done in the client,
since all paths just result in MONGO_ERROR being returned.

Diff, which includes the incorrect bson_free mentioned in ticket CDRIVER-208:

diff --git a/src/mongo.c b/src/mongo.c
index c8df093..3487488 100644
— a/src/mongo.c
+++ b/src/mongo.c
@@ -1269,16 +1269,13 @@ static int mongo_cursor_get_more( mongo_cursor *cursor ) {
data = mongo_data_append32( data, &limit );
mongo_data_append64( data, &cursor->reply->fields.cursorID );

• bson_free( cursor->reply );
  res = mongo_message_send( cursor->conn, mm );
  if( res != MONGO_OK ) { - mongo_cursor_destroy( cursor ); return MONGO_ERROR; }
  
  res = mongo_read_response( cursor->conn, &( cursor->reply ) );
  if( res != MONGO_OK ) {- mongo_cursor_destroy( cursor ); return MONGO_ERROR; }

  cursor->current.data = NULL;