cov: remove tautological #defines

R=golang-dev
CC=golang-dev, rsc
https://golang.org/cl/4941048

src/cmd/cov/tree.c

@@ -2,7 +2,7 @@
 
 /*
 Copyright (c) 2003-2007 Russ Cox, Tom Bergan, Austin Clements,
-                        Massachusetts Institute of Technology
+	Massachusetts Institute of Technology
 Portions Copyright (c) 2009 The Go Authors. All rights reserved.
 
 Permission is hereby granted, free of charge, to any person obtaining
@@ -35,9 +35,6 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 #include <libc.h>
 #include "tree.h"
 
-#define TreeNode TreeNode
-#define Tree Tree
-
 enum
 {
 	Red = 0,