http: use upper case hex in URL escaping

According to RFC 3986: "For consistency, URI producers
and normalizers should use uppercase hexadecimal digits
for all percent-encodings."  Using lower case characters
makes it incompatible with Google APIs when signing OAuth requests.

R=golang-dev, rsc1, rsc
CC=golang-dev
https://golang.org/cl/4352044

src/pkg/http/url.go

@@ -213,8 +213,8 @@ func urlEscape(s string, mode encoding) string {
 			j++
 		case shouldEscape(c, mode):
 			t[j] = '%'
-			t[j+1] = "0123456789abcdef"[c>>4]
-			t[j+2] = "0123456789abcdef"[c&15]
+			t[j+1] = "0123456789ABCDEF"[c>>4]
+			t[j+2] = "0123456789ABCDEF"[c&15]
 			j += 3
 		default:
 			t[j] = s[i]

src/pkg/http/url_test.go

@@ -490,7 +490,7 @@ var escapeTests = []URLEscapeTest{
 	},
 	{
 		" ?&=#+%!<>#\"{}|\\^[]`☺\t",
-		"+%3f%26%3d%23%2b%25!%3c%3e%23%22%7b%7d%7c%5c%5e%5b%5d%60%e2%98%ba%09",
+		"+%3F%26%3D%23%2B%25!%3C%3E%23%22%7B%7D%7C%5C%5E%5B%5D%60%E2%98%BA%09",
 		nil,
 	},
 }
@@ -519,7 +519,7 @@ type UserinfoTest struct {
 var userinfoTests = []UserinfoTest{
 	{"user", "password", "user:password"},
 	{"foo:bar", "~!@#$%^&*()_+{}|[]\\-=`:;'\"<>?,./",
-		"foo%3abar:~!%40%23$%25%5e&*()_+%7b%7d%7c%5b%5d%5c-=%60%3a;'%22%3c%3e?,.%2f"},
+		"foo%3Abar:~!%40%23$%25%5E&*()_+%7B%7D%7C%5B%5D%5C-=%60%3A;'%22%3C%3E?,.%2F"},
 }
 
 func TestEscapeUserinfo(t *testing.T) {