VideoCommon: Replace SOIL with libpng for hires textures

Source/Core/Common/Image.h

@@ -0,0 +1,15 @@
+// Copyright 2016 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <vector>
+
+#include "Common/CommonTypes.h"
+
+namespace Common
+{
+bool LoadPNG(const std::vector<u8>& input, std::vector<u8>* data_out, u32* width_out,
+             u32* height_out);
+}