I tried to split this patch as much as it goes, but still
it's quite huge.
Mostly it has many compatible structures declarations.
Lesser it contains adaptation to new native/compat sigframe duality.

The only logic that changed by this patch is the order of
creating sigframe in construct_sigframe.

Cc: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>