Disable database COMMENT field by default in all other DB Forge drivers

Signed-off-by: Zachary Flower <zach@ninjaninja.net>
diff --git a/system/database/drivers/mssql/mssql_forge.php b/system/database/drivers/mssql/mssql_forge.php
index 8d98093..315ca4b 100644
--- a/system/database/drivers/mssql/mssql_forge.php
+++ b/system/database/drivers/mssql/mssql_forge.php
@@ -74,6 +74,13 @@
 		'REAL'		=> 'FLOAT'
 	);
 
+	/**
+	 * COMMENT value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_comment			= FALSE;
+
 	// --------------------------------------------------------------------
 
 	/**