wasapi: Implement automatic stream management

Submitted by Nirbheek Chauhan @nirbheek

Link to original bug (#793059)

Description

Currently, when using wasapisrc/wasapisink, if the default source devices changes WASAPI captures and sends us silence, and if the default sink device changes WASAPI throws away all rendered audio. Starting with Windows 10, WASAPI now has automatic stream management:

https://msdn.microsoft.com/en-us/library/windows/desktop/mt784437(v=vs.85).aspx

We should implement this in such a way that this mechanism is used at runtime if running on Windows 10, and a fallback mechanism (manually switching devices) is used when running on Windows 7 or 8.