Skip float truncation test under libmysql

We don't return native types for libmysql, so this test doesn't
make sense.

ext/pdo_mysql/tests/bug79596.phpt

@@ -6,6 +6,7 @@ require_once(__DIR__ . DIRECTORY_SEPARATOR . 'skipif.inc');
 require_once(__DIR__ . DIRECTORY_SEPARATOR . 'mysql_pdo_test.inc');
 MySQLPDOTest::skip();
 if (!setlocale(LC_ALL, 'de_DE', 'de-DE')) die('skip German locale not available');
+if (!MySQLPDOTest::isPDOMySQLnd()) die('skip libmysql returns result as string');
 ?>
 --FILE--
 <?php