I need it to call sigaction from 32-bit code as kernel will
set sigframe ABI according to sigaction call ABI.
Also I will call {get,set}_thread_area to restore TLS entries.

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>