Better detection of DirectX 9 in environments like VisualStudio where the IDE installation may include some parts of DirectX but not the bits we require.
Merge branch 'feature/optional-build-directx-samples' into merge-test

* feature/optional-build-directx-samples:
  Better detection of DirectX 9 in environments like VisualStudio where the IDE installation may include some parts of DirectX but not the bits we require.