regexp tests: make some benchmarks more meaningful
The first two "Literal" tests were silly.
Also fix a naming typo in a couple of tests.

R=rsc
CC=golang-dev
https://golang.org/cl/4127045
diff --git a/src/pkg/regexp/find_test.go b/src/pkg/regexp/find_test.go
index 1690711..9909303 100644
--- a/src/pkg/regexp/find_test.go
+++ b/src/pkg/regexp/find_test.go
@@ -381,7 +381,7 @@
 	}
 }
 
-func TestFindStringSubmatchndex(t *testing.T) {
+func TestFindStringSubmatchIndex(t *testing.T) {
 	for _, test := range findTests {
 		testFindSubmatchIndex(&test, MustCompile(test.pat).FindStringSubmatchIndex(test.text), t)
 	}
@@ -452,7 +452,7 @@
 	}
 }
 
-func TestFindAllStringSubmatchndex(t *testing.T) {
+func TestFindAllStringSubmatchIndex(t *testing.T) {
 	for _, test := range findTests {
 		testFindAllSubmatchIndex(&test, MustCompile(test.pat).FindAllStringSubmatchIndex(test.text, -1), t)
 	}