Fixes the following error on travis-ci:
  CC       arch/x86/syscalls/syscall32.o
In file included from /usr/include/signal.h:28:0,
                 from /home/travis/build/0x7f454c46/criu/criu/arch/x86/include/asm/types.h:5,
                 from arch/x86/syscalls/syscall32.c:1:
/usr/include/features.h:374:25: fatal error: sys/cdefs.h: No such file or directory
 #  include <sys/cdefs.h>
                         ^
Signed-off-by: Dmitry Safonov <dsafonov@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>