MDL-17969 mssql (freetds/odbtp) native driver. Passes all the tests but:

- import record
- reset sequence
... so it's a good moment to add it.

lib/dml/mssql_native_moodle_recordset.php

@@ -0,0 +1,78 @@
+<?php
+
+// This file is part of Moodle - http://moodle.org/
+//
+// Moodle is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// Moodle is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+
+/**
+ * MSSQL specific recorset.
+ *
+ * @package    moodlecore
+ * @subpackage DML
+ * @copyright  2009 onwards Eloy Lafuente (stronk7) {@link http://stronk7.com}
+ * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
+ */
+
+require_once($CFG->libdir.'/dml/moodle_recordset.php');
+
+class mssql_native_moodle_recordset extends moodle_recordset {
+
+    protected $rsrc;
+    protected $current;
+
+    public function __construct($rsrc) {
+        $this->rsrc  = $rsrc;
+        $this->current = $this->fetch_next();
+    }
+
+    public function __destruct() {
+        $this->close();
+    }
+
+    private function fetch_next() {
+        if ($row = mssql_fetch_assoc($this->rsrc)) {
+            $row = array_change_key_case($row, CASE_LOWER);
+        }
+        return $row;
+    }
+
+    public function current() {
+        return (object)$this->current;
+    }
+
+    public function key() {
+    /// return first column value as key
+        if (!$this->current) {
+            return false;
+        }
+        $key = reset($this->current);
+        return $key;
+    }
+
+    public function next() {
+        $this->current = $this->fetch_next();
+    }
+
+    public function valid() {
+        return !empty($this->current);
+    }
+
+    public function close() {
+        if ($this->rsrc) {
+            mssql_free_result($this->rsrc);
+            $this->rsrc  = null;
+        }
+        $this->current = null;
+    }
+}