rearrange some constants.  unicode package now defines MaxRune and ReplacementChar.
utf8 package imports unicode to get those definitions.
regenerate dependencies.

R=rsc
DELTA=41  (19 added, 3 deleted, 19 changed)
OCL=34123
CL=34129
diff --git a/src/pkg/unicode/letter_test.go b/src/pkg/unicode/letter_test.go
index 13daa03..0ccb29f 100644
--- a/src/pkg/unicode/letter_test.go
+++ b/src/pkg/unicode/letter_test.go
@@ -2,9 +2,12 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package unicode
+package unicode_test
 
-import "testing"
+import (
+	"testing";
+	. "unicode";
+)
 
 var upperTest = []int{
 	0x41,