Backport of Seccomp-bpf ("mode filter") from Linux
kernel 3.8 and ChromiumOS "thirdparty" 3.4:
http://git.chromium.org/gitweb/?p=chromiumos/third_party/kernel.git

Based on backport to 3.0 by Guillaume Destuynder <kang@mozilla.com>.
See also: https://bugzil.la/790923 and https://bugzil.la/932098

The "fake packet" code in seccomp_run_filters (and the deletion of
seccomp_check_filter) avoids needing to backport invasive changes to
the BPF implementation, but there may be security implications in the
presence of untrusted filter programs.
Enable SECCOMP_FILTER on goldfish (Android emulator).