The ctrl_handler is never destroyed. We have to destroy it at request
end so we avoid leaking it and also avoid keeping a reference to
previous request memory in a next request. The latter can result in a
crash and can be demonstrated with this script and `--repeat 2`:
```php
class Test {
public function set() {
sapi_windows_set_ctrl_handler(self::cb(...));
}
public function cb() {
}
}
$test = new Test;
$test->set();
sleep(3);
```
When you hit CTRL+C in the second request you can crash.
This patch resolves both the leak and crash by destroying the
ctrl_handler after a request.
Closes GH-18231.
