Updating DboMysql to fix an issue where virtualFields that were simple

aliases to fields on other tables would end up in the wrong place.
Tests added.  Fixes #655

cake/libs/model/datasources/dbo/dbo_mysql.php

@@ -727,8 +727,8 @@ function resultSet(&$results) {
 		$j = 0;
 
 		while ($j < $numFields) {
-			$column = mysql_fetch_field($results,$j);
-			if (!empty($column->table)) {
+			$column = mysql_fetch_field($results, $j);
+			if (!empty($column->table) && strpos($column->name, '__') === false) {
 				$this->map[$index++] = array($column->table, $column->name);
 			} else {
 				$this->map[$index++] = array(0, $column->name);

cake/tests/cases/libs/model/model_read.test.php

@@ -7293,6 +7293,21 @@ function testVirtualFields() {
 		$this->assertTrue(isset($result['Author']['full_name']));
 	}
 
+/**
+ * test that virtual fields work when they don't contain functions.
+ *
+ * @return void
+ */
+	function testVirtualFieldAsAString() {
+		$this->loadFixtures('Post', 'Author');
+		$Post =& new Post();
+		$Post->virtualFields = array(
+		    'writer' => 'Author.user'
+		);
+		$result = $Post->find('first');
+		$this->assertTrue(isset($result['Post']['writer']), 'virtual field not fetched %s');
+	}
+
 /**
  * test that isVirtualField will accept both aliased and non aliased fieldnames
  *