Add db_set_charset() support for PostgreSQL and change its implementation for 'mysql'
diff --git a/system/database/drivers/mysql/mysql_driver.php b/system/database/drivers/mysql/mysql_driver.php
index 7108a6d..84f7791 100644
--- a/system/database/drivers/mysql/mysql_driver.php
+++ b/system/database/drivers/mysql/mysql_driver.php
@@ -147,7 +147,7 @@
 	 * @param	string
 	 * @return	bool
 	 */
-	public function db_set_charset($charset, $collation)
+	protected function _db_set_charset($charset, $collation)
 	{
 		return function_exists('mysql_set_charset')
 			? @mysql_set_charset($charset, $this->conn_id)