regexp: exclude exhaustive RE2 test from running under race detector.

It is an expensive test to run, and even more so with -race,
and causes timeouts on builders. It is doubtful that it would
find a race that other tests in this package wouldn't, so there
is little loss in excluding it.

Update #5837.

R=golang-dev, dave
CC=golang-dev
https://golang.org/cl/11568043

src/pkg/regexp/exec2_test.go

+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// +build !race
+
+package regexp
+
+import (
+	"testing"
+)
+
+// This test is excluded when running under the race detector because
+// it is a very expensive test and takes too long.
+func TestRE2Exhaustive(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping TestRE2Exhaustive during short test")
+	}
+	testRE2(t, "testdata/re2-exhaustive.txt.bz2")
+}

src/pkg/regexp/exec_test.go

@@ -67,13 +67,6 @@ func TestRE2Search(t *testing.T) {
 	testRE2(t, "testdata/re2-search.txt")
 }
 
-func TestRE2Exhaustive(t *testing.T) {
-	if testing.Short() {
-		t.Skip("skipping TestRE2Exhaustive during short test")
-	}
-	testRE2(t, "testdata/re2-exhaustive.txt.bz2")
-}
-
 func testRE2(t *testing.T, file string) {
 	f, err := os.Open(file)
 	if err != nil {