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.

Add a test for this function.

It doesn't matter whether or not the array is declared as a pointer or 
is declared using array subscripts - the array is still allocated by the 
unmarshalling function and so needs to be freed.

Fix a typo that caused varying arrays never to be freed.

Fix another typo with the check for conformant arrays being performed 
twice, redundantly.

imm32: ImmNotifyIMM with CPS_CANCEL fully clears the composition string. Also enable respective tests.