Fix the ia64 build error that occurs in the linux-next tree by introducing
an ia64 version of uv.h.

Additionally, clean up the usage of is_uv_system().
Signed-off-by: NDean Nelson <dcn@sgi.com>
Signed-off-by: NJack Steiner <steiner@sgi.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>