IOS: Reorganise the source files and IPC_HLE→IOS

IPC_HLE is actually IOS HLE. The actual IPC emulation is not in
IPC_HLE, but in HW/WII_IPC.cpp. So calling IPC_HLE IOS is more
accurate. (If IOS LLE gets ever implemented, it'll likely be at
a lower level -- Starlet LLE.)

This also totally gets rid of the IPC_HLE prefix in file names, and
moves some source files to their own subdirectories to make the file
hierarchy cleaner.

We're going to get ~14 additional source files with the USB PR,
and this is really needed to keep things from becoming a total pain.

Source/Core/Core/IOS/DeviceStub.h

@@ -0,0 +1,28 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <string>
+
+#include "Common/CommonTypes.h"
+#include "Core/IOS/Device.h"
+#include "Core/IOS/IPC.h"
+
+namespace IOS
+{
+namespace HLE
+{
+class CWII_IPC_HLE_Device_stub : public IWII_IPC_HLE_Device
+{
+public:
+  CWII_IPC_HLE_Device_stub(u32 device_id, const std::string& device_name);
+
+  IOSReturnCode Open(const IOSOpenRequest& request) override;
+  void Close() override;
+  IPCCommandResult IOCtl(const IOSIOCtlRequest& request) override;
+  IPCCommandResult IOCtlV(const IOSIOCtlVRequest& request) override;
+};
+}  // namespace HLE
+}  // namespace IOS