specify size of buffer and use openglstate in getteximageoes

src/core/custom_tex_cache.h

@@ -48,4 +48,4 @@ private:
     std::unordered_map<u64, CustomTexInfo> custom_textures;
     std::unordered_map<u64, CustomTexPathInfo> custom_texture_paths;
 };
-} // namespace Core
+} // namespace Core