Fifo: Create a "Fifo" namespace.

Source/Core/VideoCommon/AsyncRequests.cpp

@@ -81,7 +81,7 @@ void AsyncRequests::PushEvent(const AsyncRequests::Event& event, bool blocking)
 
 	m_queue.push(event);
 
-	RunGpu();
+	Fifo::RunGpu();
 	if (blocking)
 	{
 		m_cond.wait(lock, [this]{return m_queue.empty();});