Currently we support Win7 SP1 and later; so let installer fail on lower SP levels.

Change-Id: I807e0a04870b9eeabbfae258d68da4a1156b0408
Reviewed-on: https://gerrit.libreoffice.org/52619Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>