syscall: fix marshaling of stat messages on Plan 9
syscall: fix marshaling of stat messages on Plan 9

The order of the Qid fields was reversed. Mea culpa.

R=seed
CC=golang-dev
https://codereview.appspot.com/7231062

apparentlymart/golang,dsriram/golang,pombredanne/go-deleteme,tv42/old-go,dsriram/golang,gnanderson/go,apparentlymart/golang,gnanderson/go,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,tv42/old-go,apparentlymart/golang,apparentlymart/golang,gnanderson/go,gnanderson/go,gnanderson/go,apparentlymart/golang,dsriram/golang,apparentlymart/golang,pombredanne/go-deleteme,pombredanne/go-deleteme,dsriram/golang,gnanderson/go,gnanderson/go,tv42/old-go,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,tv42/old-go,pombredanne/go-deleteme,dsriram/golang,dsriram/golang,pombredanne/go-deleteme