into a DECIMAL instead of a double as an intermediate step.

This also reverts my previous patch as this is the real cause for the
problems with Grand Prix Legends.

Use the causality ID to determine whether this is a top-level or a 
nested (called-back) call for the purposes of IMessageFilter::HandleInComingCall.

ole32: Pass in the IID and IUnknown* of the object being executed to the server notification and message filter functions.

Store the SChannelHookCallInfo structure in the message state.

This is done by putting the ORPCTHIS data into the buffer when calling
IRpcChannelBuffer::GetBuffer on the client side and then storing the
amount we increased the buffer in a structure stored in the Handle
field. This is done to present the correct Buffer pointer to the proxy
so that it writes its data after the ORPCTHIS data.

Unmarshal the data on the server side (during RPC_ExecuteCall) and make 
sure the data is consistent according to NDR rules. Also add several 
checks on the unmarshaled data that are specified by the DCOM draft 
specification.