Core/Movie: Add ability to run code in Host context

EndPlayInput runs on the CPU thread so it can't directly call
UpdateWantDeterminism. PlayController also tries to ChangeDisc
from the CPU Thread which is also invalid. It now just pauses
execution and posts a request to the Host to fix it instead.

The Core itself also did dodgy things like PauseAndLock-ing
from the CPU Thread and SetState from EmuThread which have been
removed.

Source/Core/DolphinQt2/Main.cpp

@@ -2,6 +2,7 @@
 // Licensed under GPLv2+
 // Refer to the license.txt file included.
 
+#include <QAbstractEventDispatcher>
 #include <QApplication>
 
 #include "Core/BootManager.h"
@@ -20,6 +21,12 @@ int main(int argc, char* argv[])
 	UICommon::Init();
 	Resources::Init();
 
+	// Whenever the event loop is about to go to sleep, dispatch the jobs
+	// queued in the Core first.
+	QObject::connect(QAbstractEventDispatcher::instance(),
+	                 &QAbstractEventDispatcher::aboutToBlock,
+	                 &app, &Core::HostDispatchJobs);
+
 	MainWindow win;
 	win.show();
 	int retval = app.exec();