The current Pledge function still takes into account the deprecated
"paths" argument, which has been replaced by "execpromises".
This change has been committed to OpenBSD on the 11 December 2017:
https://marc.info/?l=openbsd-tech&m=151302727506669.
This commit updates the Pledge function interface to reflect this
change.

Fixes golang/go#26824

Change-Id: Id6255b0432cf0a33e680e342dd23c7b02d0aa78f
Reviewed-on: https://go-review.googlesource.com/127762
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>