Description:
------------
Windows SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE

Using this file:

    <?php
    symlink('a.php', 'b.php');

I get this result:

    PS C:\php> php a.php
    Warning: symlink(): Permission denied in C:\php\a.php on line 2

I am not running as admin, but I do have developer mode enabled:

<https://howtogeek.com/292914/what-is-developer-mode-in-windows-10>

Since December 2016, admin rights are not required to create a symlink, as long
as the application uses the flag `SYMBOLIC_LINK_FLAG_ALLOW_UNPRIVILEGED_CREATE`:

<https://blogs.windows.com/windowsdeveloper/2016/12/02/symlinks-windows-10>

Note that other programming languages are already doing this. For example
Python:

<https://github.com/python/cpython/blob/1f764531/Modules/winreparse.h#L50>

Dart:

<https://github.com/dart-lang/sdk/blob/a677c245/runtime/bin/file_win.cc#L430>

Go:

<https://github.com/golang/go/blob/dd150176/src/internal/syscall/windows/symlink_windows.go#L13>

Nim:

<https://github.com/nim-lang/Nim/blob/af27e6bd/lib/pure/os.nim#L2417-L2419>