x/sys/unix: added linux/mips{,le} support

Change-Id: Ibf7a9e16ba0e1dde922748a34d61e197a985ed40
Reviewed-on: https://go-review.googlesource.com/33952
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
13 files changed