Merged requested to merge seungha.yang/gst-plugins-bad:wasapi-device-monitor into master
Adding IMMDeviceEnumerator::RegisterEndpointNotificationCallback in order to support device monitoring. On OnDeviceAdded(), OnDeviceRemoved(), and OnDefaultDeviceChanged() callback, wasapi device provider implementation will enumerate devices again and will notify newly added and removed device via GstDeviceProvider API.
As a bonus point, this IMMDeviceEnumerator abstraction object will spawn a dedicated internal COM thread, so various COM thread related issues of WASAPI plugin can be resolved by this commit.
Fixes: #1649 (closed) Fixes: #1110 (closed)