docs/examples/httpput.c: fix build for MSVC

"Dan Fandrich" <dan@coneharvesters.com> wrote:

>> But I'm not sure <unistd.h> is needed at all.
>
> It's needed for close(2). But the only reason that's needed is because fstat
> is used instead of stat(2); if you fix that, then you could remove that
> include altogether.

Okay. I've tested the following with MSVC and MingW. htttput.c now
simply uses stat():