dinput: Implement DIPROP_KEYNAME property for keyboard device

[Vitaliy Margolen]

Sergey Khodych wrote:
>> In ascii function you are calling unicode function and copying it's output 
>> (unicode string) to the ascii string buffer. This is wrong. Also because 
>> these functions deal with strings you have to implement both ascii and 
>> unicode functions at the same time. You can't forward one to the other.
> Variable ps->wsz not a ascii string buffer because wsz field of struct
> DIPROPSTRING has type WCHAR[MAX_PATH]. Function
> IDirectInputDevice8::GetProperty works only with unicode strings.
> 
No, there are 2 separate implementations - one ascii another unicode. During 
the object creation one would specify either ascii or unicode RIID.

Vitaliy.