Bug 920372 - Import Chromium seccomp-bpf compiler, rev 4c08f442d2588a2c7cfaa117a55bd87d2ac32f9a. r=kang

Newly imported:
* sandbox/linux/seccomp-bpf/
* sandbox/linux/sandbox_export.h
* base/posix/eintr_wrapper.h

Updated:
* base/basictypes.h
* base/macros.h

At the time of this writing (see future patches for this bug) the only
things we're using from sandbox/linux/seccomp-bpf/ are codegen.cc and
basicblock.cc, and the header files they require.  However, we may use
more of this code in the future, and it seems cleaner in general to
import the entire subtree.
Bug 920372 - Use Chromium seccomp-bpf compiler to dynamically build sandbox program. r=kang
Bug 920372 - Allow tgkill only for threads of the calling process itself. r=kang
Bug 920372 - Fix socketcall whitelisting on i386. r=kang