all: fix misprints in comments

These were found by grepping the comments from the go code and feeding
the output to aspell.

Change-Id: Id734d6c8d1938ec3c36bd94a4dbbad577e3ad395
Reviewed-on: https://go-review.googlesource.com/10941
Reviewed-by: Aamir Khan <syst3m.w0rm@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/src/net/url/example_test.go b/src/net/url/example_test.go
index e55c1aa..af4ad0b 100644
--- a/src/net/url/example_test.go
+++ b/src/net/url/example_test.go
@@ -47,7 +47,7 @@
 	// Sending a literal '%' in an HTTP request's Path
 	req := &http.Request{
 		Method: "GET",
-		Host:   "example.com", // takes precendence over URL.Host
+		Host:   "example.com", // takes precedence over URL.Host
 		URL: &url.URL{
 			Host:   "ignored",
 			Scheme: "https",