And `$x = !$x`

Noticed while working on GH-4912

The included test would not emit undefined variable errors in php 8.0
with opcache enabled. The command used:

```
php -d zend_extension=opcache.so --no-php-ini -d error_reporting=E_ALL \
    -d opcache.file_cache= -d opcache.enable_cli=1  test.php
```

https://www.php.net/manual/en/function.get-headers.php#refsect1-function.get-headers-examples
shows that it will return string keys when the second argument is
non-zero. I've verified that this is the case.

This bug was there since the initial commit in c88ffa9a567.

Closes GH-4702.

It can return false if the resource type is wrong.

```
php > var_export(hash_update_stream(hash_init('md5'),
        imagecreate(1,1)));

Warning: hash_update_stream(): supplied resource is not a valid stream
resource in php shell code on line 1
false
```

The return types were initially added in
c88ffa9a5673cb3141660626ba1921671f0b84d6

Backported from a1a8d144854acb1c891cf0c21abb0f612b1d8de7
https://www.php.net/manual/en/function.passthru.php#refsect1-function.passthru-returnvalues

`passthru()` is false with invalid args
`passthru('command')` is null.

This can also return an array. See
https://www.php.net/manual/en/function.time-nanosleep.php#refsect1-function.time-nanosleep-returnvalues

> If the delay was interrupted by a signal, an associative array will be
returned with the components:
>
> - seconds - number of seconds remaining in the delay
> - nanoseconds - number of nanoseconds remaining in the delay

Sending a SIGUSR1 to the below program would trigger this behavior.

```
pcntl_signal(\SIGUSR1, function ($signo, $signinfo) {
    echo "Handling a signal $signo\n";
});
echo "Sleeping for 100 seconds\n";
var_export(time_nanosleep(100, 0));
```

The incomplete signature existed since c88ffa9a5.
No phpt tests existed for time_nanosleep returning an array

There are a few parts here:
 * opcache should not be blocking signals while invoking compile_file,
   otherwise signals may remain blocked on a compile error. While at
   it, also protect SHM memory during compile_file.
 * We should deactivate Zend signals at the end of the request, to make
   sure that we gracefully recover from a missing unblock and signals
   don't remain blocked forever.
 * We don't use a critical section in deactivation, because it should
   not be necessary. Additionally we want to clean up the signal queue,
   if it is non-empty.
 * Enable SIGG(check) in debug builds so we notice issues in the future.