This was causing an assertion violation in Ui::PostponeCall.
- Add a generic Core::QtSignalProducer to convert Qt signals to rpl::producer.
- Track event loop nesting inside QtSignalProducer.
- Use QtSignalProducer for QWindow::activeChanged tracking.
For some reason deleteLater() called for the tooltip from the main
window deactivation signal is really handled only on app quit :/
So now we use InvokeQueued(p, [p] { delete p; }); there instead.
Fixes#3461
Use Qt::Dialog instead of Qt::Tool which works better with window
activation / deactivation handling.
Stop displaying the panel on all spaces when the call is established.
Currently the build without implicitly included precompiled header
is not supported anyway (because Qt MOC source files do not include
stdafx.h, they include plain headers).
So when we decide to support building without implicitly included
precompiled headers we'll have to fix all the headers anyway.
