Added support for dynamic d3dcompile load

If you really want to use d3dcompile, then I think its better to find the most recent d3dcompile you have on your computer and load its D3DCompile function.
This process is now automatically handled. Just define  the right Preprocessor.

ImGui/impls/imgui_impl_dx12.cpp

@@ -468,6 +468,12 @@ bool    ImGui_ImplDX12_CreateDeviceObjects()
     psoDesc.SampleDesc.Count = 1;
     psoDesc.Flags = D3D12_PIPELINE_STATE_FLAG_NONE;
 
+#ifdef USE_D3DCOMPILE
+    decltype(D3DCompile)* D3DCompile = load_d3dcompile();
+    if (D3DCompile == nullptr)
+        return false;
+#endif
+
     // Create the vertex shader
     {
 #ifdef USE_D3DCOMPILE
@@ -546,6 +552,10 @@ bool    ImGui_ImplDX12_CreateDeviceObjects()
 #endif
     }
 
+#ifdef USE_D3DCOMPILE
+    unload_d3dcompile();
+#endif
+
     // Create the blending setup
     {
         D3D12_BLEND_DESC& desc = psoDesc.BlendState;