vioscsi: Add downlevel targets to vioscsi.vcxproj
vioscsi: Add downlevel targets to vioscsi.vcxproj

This commit adds Win7 and Vista targets to the VS project
file. Two unused local variables are removed, found by the
newer compiler.

virtio-win/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,gnif/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,ladipro/kvm-guest-drivers-windows,YanVugenfirer/virtio-win-arm,virtio-win/kvm-guest-drivers-windows,YanVugenfirer/virtio-win-arm,virtio-win/kvm-guest-drivers-windows,ladipro/kvm-guest-drivers-windows,ladipro/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/virtio-win-arm,YanVugenfirer/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,virtio-win/kvm-guest-drivers-windows,gnif/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/kvm-guest-drivers-windows,gnif/kvm-guest-drivers-windows,daynix/kvm-guest-drivers-windows,YanVugenfirer/virtio-win-arm,daynix/kvm-guest-drivers-windows,ladipro/kvm-guest-drivers-windows,gnif/kvm-guest-drivers-windows,vrozenfe/kvm-guest-drivers-windows