Fix tests - some functions are platform dependent

Author: petk

ext/readline/tests/bug72538.phpt

@@ -2,6 +2,10 @@
 Bug #72538 (readline_redisplay crashes php)
 --EXTENSIONS--
 readline
+--SKIPIF--
+<?php
+if (!function_exists("readline_redisplay")) die("skip readline_redisplay not available");
+?>
 --FILE--
 <?php
 

ext/readline/tests/libedit_callback_handler_install_001.phpt

@@ -3,6 +3,8 @@ readline_callback_handler_install(): Basic test
 lsan disabled due to a leak on ubuntu focal only.
 --EXTENSIONS--
 readline
+--SKIPIF--
+<?php if (!function_exists('readline_callback_handler_install')) die("skip readline_callback_handler_install not available"); ?>
 --INI--
 zend.signal_check=0
 --ENV--

ext/readline/tests/libedit_callback_handler_remove_001.phpt

@@ -3,6 +3,10 @@ readline_callback_handler_remove(): Basic test
 lsan disabled due to a leak on ubuntu focal only.
 --EXTENSIONS--
 readline
+--SKIPIF--
+<?php
+if (!function_exists('readline_callback_handler_remove')) die("skip readline_callback_handler_remove not available");
+?>
 --INI--
 zend.signal_check=0
 --ENV--