godoc: fix missing name change

Fixes godoc text mode (i.e., URL?m=text).

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5545043

lib/godoc/package.html

@@ -44,7 +44,7 @@
 {{end}}
 {{with .PDoc}}
 	<h2 id="Overview">Overview</h2>
-	<!-- PackageName is printed as title by the top-level template -->
+	<!-- The package's Name is printed as title by the top-level template -->
 	{{if $.IsPkg}}
 		<p><code>import "{{html .ImportPath}}"</code></p>
 	{{end}}

lib/godoc/package.txt

@@ -4,7 +4,7 @@
 
 */}}{{with .PDoc}}{{if $.IsPkg}}PACKAGE
 
-package {{.PackageName}}
+package {{.Name}}
     import "{{.ImportPath}}"
 
 {{else}}COMMAND DOCUMENTATION