d3dx9: Add D3DXFrameFind stub.

[Nikolay Sivov]

On 12.08.2016 13:00, Andrey Gusev wrote:
> +D3DXFRAME * WINAPI D3DXFrameFind(const D3DXFRAME *frame_root, const char *name)
> +{
> +    FIXME("frame_root %p, name %s stub!\n", frame_root, debugstr_a(name));
> +
> +    return NULL;
> +}

This looks trivial enough to implement. It's probably just going from
pFrameFirstChild -> pFrameSibling. The question is does it check
grandchildren, but it's easy to test.