Kernel/HLE: Use a mutex to synchronize access to the HLE kernel state between the cpu thread and any other possible threads that might touch the kernel (network thread, etc).

This mutex is acquired in SVC::CallSVC, ie, as soon as the guest application enters the HLE kernel, and should be acquired by the aforementioned threads before modifying kernel structures.

src/core/hle/lock.cpp

@@ -0,0 +1,11 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <core/hle/lock.h>
+
+namespace HLE {
+std::mutex g_hle_lock;
+}