This makes sure the windows version of these functions behave
more like the posix version. The posix *snprintf returns how
much would have been written if the buffer had been large
enough, which we don't know easily in the windows versions.
This basically means that we can assume that the return value is
>= 0 now, which can simplify the calling code.
Windows Phone lacks the old CreateThread/beginthreadex APIs for
creating threads. (Technically, the functions still do exist,
but they aren't officially supported and aren't visible in the
headers when targeting Windows Phone.)
Building code that uses the Windows Runtime language extensions
requires building with the -ZW option.
