Unmarshals a BSTR object from the RPC buffer.
BYTE * __RPC_USER BSTR_UserUnmarshal(
[in] Points to data used by RPC.
[in] Points to the current buffer. This pointer may or may not be aligned on entry.
[out] Points to the BSTR object that will be unmarshaled.
The return value obtained from the returned HRESULT is one of the following.
Insufficient memory for this function to perform.