Fixes these complaints from vet:

cmd/compile/internal/gc/noder.go:32: cmd/compile/internal/syntax.Error composite literal uses unkeyed fields
cmd/compile/internal/gc/noder.go:1035: cmd/compile/internal/syntax.Error composite literal uses unkeyed fields
cmd/compile/internal/gc/noder.go:1051: cmd/compile/internal/syntax.Error composite literal uses unkeyed fields
cmd/compile/internal/syntax/parser_test.go:182: possible formatting directive in Error call
net/http/client_test.go:1334: possible formatting directive in Fatal call

Change-Id: I5f90ec30f3c106c7e66c92e2b6f8d3b4874fec66
Reviewed-on: https://go-review.googlesource.com/33133
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>