Msi remote viewer

Successfully generated the msi [0] for remote-viewer with these changes.

I'm still spending some time around wasapi audio backend as that got improvements in GStreamer but not yet compatible with spice-gtk code and would possibly introduce some regressions even feature wise, such as volume setting.

[0] https://people.freedesktop.org/~victortoso/msi-testing/virt-viewer-x64-8.0-on-31072018.msi