include: Add d3dx10.h file

[Nikolay Sivov]

On 26.10.2015 20:50, Matteo Bruni wrote:
> 2015-10-25 20:10 GMT+01:00 Nikolay Sivov <bunglehead at gmail.com>:
>>> +#include "d3dx10.h"
>>
>>
>> This doesn't look right.
>
> For the records, that line is also in MS's d3dx10.h. Of course it's
> useless and we shouldn't replicate the same mistake.
>
>

That raises a question of what else was copied directly from SDK header.