core: Allocate CoreEntry (except arch) with single xmalloc

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
core: Allocate x76 core entry with single (almost) xmalloc

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>