RFC: KUSER_SHARED_DATA update patch to fix bug 29168

[Joey Yandle]

> 
> If user_shared_data was written by wineserver and mapped read-only to
> wine processes there was no need to create separate threads in wine
> processes. As I know Windows is sharing this structure and is updating
> it in kernel mode so wine behavior was similar if was updated by
> wineserver.
> 

Agreed, this is the ideal solution.  I'm just not sure how to do so
while maintaining the virtual address mapping required for user_shared_data.