Implemented putenv()

[comm644]

Please integrate putenv() function and add unit-tests. I did't understood how to add unit-tests.

test code:

<?php


$locale = 'ru_RU.UTF-8';
putenv('LC_ALL=' . $locale);

$result = getenv("LC_ALL");

if  ($result !== $locale ) throw new \RuntimeException("putenv() does not work");
echo "ok\n";