[ros-kernel] Suggested implementation ideas for the various WndProc, CallWndProc etc fixes

[Jonathan Wilson]

> Why can't the kernel/executive simply free them when the process
> terminates, regardless of whether normal termination occurs or not?
Well any time that Win32kProcessCallback() is called with a value of 
"process is being destroyed", then any structures owned by the current 
process will be zeroed out ready for reuse.