[MS-RDPEA]: Audio Output Virtual Channel Extension

[elmarco]

Implement https://winprotocoldoc.blob.core.windows.net/productionwindowsarchives/MS-RDPEA/%5bMS-RDPEA%5d.pdf

(heads up, as I am also working on this)

• [x] rdpsnd/pdu
• [ ] client
• [x] server