[#213] Add dedicated close() method to Query class.

This commit exposes the functionality of _close() in a
backwards-compatible way.

close() should be used when executing multiple GenQuery2 queries and the
resultsets are no longer needed. This allows policy writers to avoid
memory exhaustion when using GenQuery2.

Author: korydraughn

genquery.py

@@ -378,6 +378,14 @@ def _close(self):
         self.gqo = None
         self.cti = None
 
+    def close(self):
+        """Close the query.
+
+        When GenQuery1 is used, prevents filling the statement table.
+        When GenQuery2 is used, closes the resultset.
+        """
+        self._close()
+
     def first(self):
         """Get exactly one result (or None if no results are available)."""
         result = None