chore(namespaces): start adding per arch syscall numbers

I didn't move TIOCGPTN since it looks from a brief glance at the kernel
that the archs that matter right now (arm, x86) share the same
definition.

Docker-DCO-1.1-Signed-off-by: Brandon Philips <brandon.philips@coreos.com> (github: philips)
Merge pull request #9 from philips/add-libcontainer

chore(namespaces): start adding per arch syscall numbers