[Dnsapi.dll] Implement Dnsapi.dll

[MattK]

> Please submit a seperate patch for the windns.h header file.
In order for the patch to compile you need the windns.h header.

> Hmmm.  The Windows Platform SDK doesn't define this function as
WINAPI.
In WinDNS.h in the PSDK include directory, it is declared as BOOL
WINAPI.

> Maybe cdecl instead, if the Platform SDK header is right?
Nope. WINAPI is just another name for __stdcall.

I'll do everything you suggested. If you want to compile the patch you
will need the separate patch for windns.h.