[ticket/17148] Fix sql_table_exists() error for PostgreSQL 9.3 and earlier

PostgreSQL 9.3 and earlier versions don't support Empty SELECT lists
(support was added since v. 9.4).
Also add PostgreSQL 9.3 tests as earlier images fail in current tests env.

PHPBB3-17148

phpBB/phpbb/db/tools/postgres.php

@@ -102,7 +102,7 @@ class postgres extends tools
 	function sql_table_exists($table_name)
 	{
 		$sql = "SELECT CAST(EXISTS(
-			SELECT FROM information_schema.tables
+			SELECT * FROM information_schema.tables
 				WHERE table_schema = 'public'
 					AND table_name   = '" . $this->db->sql_escape($table_name) . "'
 			) AS INTEGER)";