Add some support for the shared page (currently 3d slider is implemented)

src/core/hle/shared_page.h

@@ -0,0 +1,26 @@
+// Copyright 2015 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+/**
+ * The shared page stores various runtime configuration settings. This memory page is
+ * read-only for user processes (there is a bit in the header that grants the process
+ * write access, according to 3dbrew; this is not emulated)
+ */
+
+#include "common/common_types.h"
+
+////////////////////////////////////////////////////////////////////////////////////////////////////
+
+namespace SharedPage {
+
+template <typename T>
+void Read(T &var, const u32 addr);
+
+void Set3DSlider(float amount);
+
+void Init();
+
+} // namespace