Adds method to read device data including timing information

[gucki]

As I needed to mix multiple streams I needed the timing information. For backwards compatibility, this PR more or less simply duplicates the existing method and additionally returns the timing information.

[HEnquist]

Thanks! I think this could just as well be added to the existing method instead of adding a second one. That's a breaking change, but a small one that is trivial to handle.
And when anyway making changes, why not return both the position values?

HRESULT GetBuffer(
  [out] BYTE   **ppData,
  [out] UINT32 *pNumFramesToRead,
  [out] DWORD  *pdwFlags,
  [out] UINT64 *pu64DevicePosition,
  [out] UINT64 *pu64QPCPosition
);