Description:
------------
Need to be able to set the location of the temporary directory for a VirtualHost using php_admin_value.

This is especially important when you have multiple VirtualHosts that are locked down with open_basedir so that they are not able to read the files in the currently shared temporary directory.

tempnam() and sys_get_temp_dir() should pull the value from this PHP setting so that no code modifications are needed. For backward compatibility, the current default value of the temporary directory can be used to set the default value for the PHP setting.

Test script:
---------------
<?php
// Make sure to put this line in your vhost config!
// php_admin_value tmp_dir "/www/myvhost/tmp"
//
// Create a temporary file in the temporary 
// files directory using sys_get_temp_dir()
echo sys_get_temp_dir() . PHP_EOL;
echo tempnam(null, 'Tux') . PHP_EOL;
?>

Expected result:
----------------
/www/myvhost/tmp
/www/myvhost/tmp/TuxDRhRIg


Actual result:
--------------
/tmp
/tmp/TuxDRhRIg