stage 2 of replacing usage of various checks for the windows platform
with the compiler-defined '_WIN32' macro

In this stage we focus on replacing usage of the WIN macro

Change-Id: Ie8a4a63198a6de96bd158ecd707dadafb9c8ea84
Reviewed-on: https://gerrit.libreoffice.org/22393Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noelgrandin@gmail.com>