Wiki: We could add optional tips to remove the DirectX SDK dependency

[rumia-san]

Since the Irrlicht supports OpenGL, the DirectX SDK is not a required dependency.
Just modify the windows filter in premake/irrlicht/premake5.lua

    filter { "system:windows" }
        defines { "_IRR_WCHAR_FILESYSTEM", "NO_IRR_COMPILE_WITH_DIRECT3D_9_", "NO_IRR_COMPILE_WITH_DIRECTINPUT_JOYSTICK_" }
        links { "imm32" }

rumia-san/ygopro@65808d1

So that we don't need to download and install DirectX SDK. We could add optional tips for this.

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就是DirectX SDK不是必需的依赖，只要irrlicht有NO_IRR_COMPILE_WITH_DIRECT3D_9_和NO_IRR_COMPILE_WITH_DIRECTINPUT_JOYSTICK_这两个宏，编译就不需要DirectX SDK了，可以在WIKI里加个提示，可能会有像我一样不想下载旧版directx sdk的人……
当然，system.conf里use_d3d只能写成0了，或者像我一样把代码写死成opengl