This patch adds necessary support for vcontext merge between

This patch adds necessary support for vcontext merge between
para and vti side. Per Dan's good suggestion, all the changes
are refined into ia64 specific. Accompanied with xeno patches
and a bit libxc change, xen0 + xenU can still work again.

Signed-off-by Eddie Dong <eddie.dong@intel.com>
Signed-off-by Kevin Tian <kevin.tian@intel.com>
Signed-off-by Fred Yang <fred.yang@intel.com>