Description:
------------
I've noticed that some errors in stream_socket_client()s connection don't populate errstr with an error. As far as I can tell, errno is always populated.

The most consistent case I've found for this if when the error code is 16 - $errstr SHOULD be "Device or resource busy" (according to some googling), however, it is empty.

I've also come across many errono's that are > 127 and have no errstr. e.g. 5736689

Reproduce code:
---------------
Unless someone knows how to reproduce "Device or resource busy", then I can't create any code to reproduce errno 16 having no errstr.

I can reproduce the oddly high errno's (with no errstr) as the example above appears to be for invalid URLs:

<?php
$stream = stream_socket_client('tcp://tinyu:80', $errno, $errstr);
echo "$errno\n";
echo "'$errstr'\n";

Expected result:
----------------
Not sure what the error number *should* be, possibly 22 (EINVAL), Invalid argument. I'll go with that:

22
'Invalid argument'

Actual result:
--------------
5736689
''