- Add vm_locking.h and vm_reservation.h and move relevant functions
and types to these headers.
- Change include order and make vm_ptr.h, vm_var.h and vm_ref.h headers
usable invidually and them including vm.h instead of other way around
- Because usage of vm::ptr now requires including vm_ptr.h instead of
vm.h updated multiple #includes
- Added additional #includes to vm_reservation.h and vm_locking to
where vm::reservation_* and locking related functions are used
