Impact: search sys-exec-tbl-32.c for compatible tasks.

Rename task_in_compat_mode to arch_task_compatible and use it in
find_syscall for 64-bit to check compatible task's syscall nr.
It still will not execute syscall in 32-tasks, as we still do not
have 32-bit pie (arch_can_dump_task will return false for these tasks).

NOTE: be sure to `make mrproper` on criu directory before applying this
patch, as before `criu/arch/x86/sys-exec-tbl.c` was autogenerated,
it will make conflict if you try to apply this patch on dirty directory.
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>