rpcrt4: Call NdrCorrelationInitialize and NdrCorrelationFree from NdrClientCall2 if new correlation descriptors have been specified.

Mask out RPC_VALID_FLAGS_BIT from ProcNum when it is used to build a 
packet to send to the server.

ole32: Fix memory leaks caused by not calling the channel hook function when extension_size is zero.

Instead free the allocated memory outside of the channel hook function.

ole32: Shortcut the RPC runtime for allocation of the message when processing the COM call by just sending a message to a window in the process.

ole32: Clear the RPC_FLAGS_VALID_BIT flag from the RPC_MESSAGE ProcNum when shortcutting the RPC runtime.

The "cannot be null" attibute is applied to a parameter if and only if 
it is in-only.

Add some tests for this.