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/regexp/exec_test.go

@@ -673,7 +673,7 @@ func benchmark(b *testing.B, re string, n int) {
 	b.SetBytes(int64(n))
 	for i := 0; i < b.N; i++ {
 		if r.Match(t) {
-			panic("match!")
+			b.Fatal("match!")
 		}
 	}
 }