Support handing out association group IDs.

There are other cases where calls to Free functions can be omitted (such 
as types always unmarshalled using buffer memory with no embedded 
pointers), but these are easier dealt with inside the relevent case in 
write_remoting_arg.

This partially reverts commit 6e9fea22.
16-bit and 32-bit clipboard handles aren't interchangeable.

advapi32: Fix undocumented behaviour in ReqQueryValueEx when 'count' and 'type' point to the same address.