It is unprecedented to add tests to package syscall, especially
system-specific ones. Not a policy worth changing right before Go 1
is cut.

The sole existing test, passfd_test.go, contains the line
        // +build linux darwin probablyfreebsd probablyopenbsd
which argues that this is not a subject to be undertaking likely.
Note that passfd_test.go also went in just now. It's the only test
in syscall.

Deleting for now, will reconsider after Go 1.

R=golang-dev, bradfitz, r, dsymonds
CC=golang-dev
https://golang.org/cl/5846063