gtk: Add property to create a window and only dispatch to main thread if that is set
Submitted by Sebastian Dröge @slomo
Link to original bug (#755612)
Description
See summary. Dispatching to the main thread and blocking, especially during state changes, can easily cause deadlocks. Currently we only do that because of the window that is created by the sinks if the user did not embed the widget anywhere. No normal application needs this but all applications now have to live in fear of deadlocks.
Version: 1.5.90