win32: tolerate extra error flags on Vista
win32: tolerate extra error flags on Vista

This should not adversely affect LibVLC: more errors cases will lead to
error code returns instead of abnormal termination. It is not strictly
semantically correct though (update to Win7 or above if you care).

shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,xkfz007/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc,xkfz007/vlc,xkfz007/vlc,xkfz007/vlc,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,shyamalschandra/vlc,vlc-mirror/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,vlc-mirror/vlc