To restore SAS we have two ways:
- call for sigaltstack explicitly in restorer.c right before we call for sigreturn
- pass stack value to sigreturn call and allow the kernel to restore stack for us

Since second way is a simplier one -- we stick with it.

[alekskartashov@: use RT_SIGFRAME_UC]
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
CC: Alexander Kartashov <alekskartashov@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>