This change changes and documents the (previously undocumented) behavior of Used
to "RAM used by programs".
We also remove the undocumented and unused Shared field of that struct.
So with this change in place, the VirtualMemoryStruct contains:
* three human-consumable fields for Total, Used and Available memory
* one human-consumable UsedPercentage field
* a number of kernel specific fields
James Nugent