godoc: update appinit.go, apply !appengine build constrain to main.go

R=adg, dsymonds
CC=golang-dev
https://golang.org/cl/5969063

src/cmd/godoc/appinit.go

@@ -17,9 +17,12 @@ import (
 )
 
 func serveError(w http.ResponseWriter, r *http.Request, relpath string, err error) {
-	contents := applyTemplate(errorHTML, "errorHTML", err) // err may contain an absolute path!
 	w.WriteHeader(http.StatusNotFound)
-	servePage(w, relpath, "File "+relpath, "", "", contents)
+	servePage(w, Page{
+		Title:    "File " + relpath,
+		Subtitle: relpath,
+		Body:     applyTemplate(errorHTML, "errorHTML", err), // err may contain an absolute path!
+	})
 }
 
 func init() {

src/cmd/godoc/main.go

@@ -23,6 +23,8 @@
 //	godoc crypto/block Cipher NewCMAC
 //		- prints doc for Cipher and NewCMAC in package crypto/block
 
+// +build !appengine
+
 package main
 
 import (