Update kfw installer OS version checks

Require XP SP3 or Vista SP2 or Windows 7 or Server 2003 or Server 2008

Signed-off-by: Kevin Wasserman <kevin.wasserman@painless-security.com>

https://github.com/krb5/krb5/commit/00f5923dd95dac8d98d4058887d144602bbd1f9f
Author: Kevin Wasserman <kevin.wasserman@painless-security.com>
Committer: Ben Kaduk <kaduk@mit.edu>
Commit: 00f5923dd95dac8d98d4058887d144602bbd1f9f
Branch: master
 src/windows/installer/wix/kfw.wxs               |    4 +++-
 src/windows/installer/wix/lang/strings_1033.wxl |    4 +++-
 2 files changed, 6 insertions(+), 2 deletions(-)