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

[Jonathan Wilson]

Well the way I implemented it is that cleanup happens in 
Win32kProcessCallback, i.e. when this is called with a Create parameter of 
FALSE, it cleans up any structures "owned" by the process.
Memory for the structures is allocated using ExAllocatePool(PagedPool) and 
deleted with ExFreePool.