Description:
------------
Unlike the standard open_basedir, Runkit_Sandbox does not support multiple paths 
separated by the PATH_SEPARATOR (e.g. "/foo:/bar")

Test script:
---------------
<?php
$sandbox = new Runkit_Sandbox(
    array(
        "open_basedir" => sys_get_temp_dir() . PATH_SEPARATOR .getcwd()
    )
);

$sandbox->eval('var_dump(ini_get("open_basedir"));'); // string(1) "" (== chr(1))

// vs.

$sandbox = new Runkit_Sandbox(
    array(
        "open_basedir" => sys_get_temp_dir()
    )
);
$sandbox->eval('var_dump(ini_get("open_basedir"));'); // string(4) "/tmp"

Expected result:
----------------
The same as with regular PHP, that both (any number of) paths is accessible, and 
any paths below them, but none above.