Cleanup semaphore<> (sema.h) and mutex.h (shared_mutex)

Remove semaphore_lock and writer_lock classes, replace with std::lock_guard
Change semaphore<> interface to Lockable (+ exotic try_unlock method)

rpcs3/rpcs3qt/log_frame.cpp

@@ -331,7 +331,7 @@ void log_frame::CreateAndConnectActions()
 		std::string text = m_tty_input->text().toStdString();
 
 		{
-			std::lock_guard<std::mutex> lock(g_tty_mutex);
+			std::lock_guard lock(g_tty_mutex);
 
 			if (m_tty_channel == -1)
 			{