update dear imgui from 1.92.2b-docking to 1.92.6-docking

libs/imgui/backends/imgui_impl_dx12.h

@@ -25,6 +25,12 @@
 #include <dxgiformat.h> // DXGI_FORMAT
 #include <d3d12.h>      // D3D12_CPU_DESCRIPTOR_HANDLE
 
+// Clang/GCC warnings with -Weverything
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wold-style-cast" // warning: use of old-style cast
+#endif
+
 // Initialization data, for ImGui_ImplDX12_Init()
 struct ImGui_ImplDX12_InitInfo
 {
@@ -65,7 +71,7 @@ IMGUI_IMPL_API bool     ImGui_ImplDX12_Init(ID3D12Device* device, int num_frames
 IMGUI_IMPL_API bool     ImGui_ImplDX12_CreateDeviceObjects();
 IMGUI_IMPL_API void     ImGui_ImplDX12_InvalidateDeviceObjects();
 
-// (Advanced) Use e.g. if you need to precisely control the timing of texture updates (e.g. for staged rendering), by setting ImDrawData::Textures = NULL to handle this manually.
+// (Advanced) Use e.g. if you need to precisely control the timing of texture updates (e.g. for staged rendering), by setting ImDrawData::Textures = nullptr to handle this manually.
 IMGUI_IMPL_API void     ImGui_ImplDX12_UpdateTexture(ImTextureData* tex);
 
 // [BETA] Selected render state data shared with callbacks.
@@ -77,4 +83,8 @@ struct ImGui_ImplDX12_RenderState
     ID3D12GraphicsCommandList*  CommandList;
 };
 
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+
 #endif // #ifndef IMGUI_DISABLE