all: fixed various typos

(Semi-automatically detected.)

R=golang-dev, remyoudompheng, r
CC=golang-dev
https://golang.org/cl/5715052
diff --git a/src/pkg/net/http/httputil/persist.go b/src/pkg/net/http/httputil/persist.go
index 32f4662..507938a 100644
--- a/src/pkg/net/http/httputil/persist.go
+++ b/src/pkg/net/http/httputil/persist.go
@@ -383,7 +383,7 @@
 	// Make sure body is fully consumed, even if user does not call body.Close
 	if lastbody != nil {
 		// body.Close is assumed to be idempotent and multiple calls to
-		// it should return the error that its first invokation
+		// it should return the error that its first invocation
 		// returned.
 		err = lastbody.Close()
 		if err != nil {