Move more helpers to seccomp-bpf-helpers.

Extract more code from content/common/sandbox_seccomp_bpf_linux.cc
and move it to sandbox/linux/seccomp-bpf-helpers/

BUG=325535
NOTRY=true
R=jorgelo@chromium.org

Review URL: https://codereview.chromium.org/98373007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238994 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 238994