syscall: (*Proc).Call should return nil error when no error occurs Fixes issue 4686.
syscall: (*Proc).Call should return nil error when no error occurs
Fixes issue 4686.

R=alex.brainman, rsc
CC=golang-dev
https://codereview.appspot.com/7174047
abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go,abustany/go