panics: use the new facilities of testing.B instead

Lots of panics go away.
Also fix a name error in html/template.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5498045

src/pkg/encoding/gob/timing_test.go

@@ -39,7 +39,7 @@ func benchmarkEndToEnd(r io.Reader, w io.Writer, b *testing.B) {
 func BenchmarkEndToEndPipe(b *testing.B) {
 	r, w, err := os.Pipe()
 	if err != nil {
-		panic("can't get pipe:" + err.Error())
+		b.Fatal("can't get pipe:", err)
 	}
 	benchmarkEndToEnd(r, w, b)
 }