misc/cgo/test: test recursive internal OS thread lock
misc/cgo/test: test recursive internal OS thread lock

This would have failed with CL 11663043.

R=golang-dev, bradfitz
CC=golang-dev
https://codereview.appspot.com/11480045

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